Archives Infernationales de Physiologie, de Biochimie et de Biophysique, 1993, 101, 245-247 245

ReCu le 5 decernbre 1991

The effect of nifedipine and verapamil on rhythmic contractions of human isolated ureter

BY

A. SAHIN, I. ERDEMLI (I), M. BAKKALOGLU, A. ERGEN, I. BASAR and D. REMZI

[Haceltepe Universily, School o f Medicine, Department of Urology and School of Pharmacy, Depariment of Pharmacology ( I ) , Ankara, Tiirkiye]

(2 figures)

The effect of calcium antagonists nifedipine and verapamil on spontaneous rhythmic con- tractions of human isolated ureter obtained from donor subjects undergoing kidney transplan- tation was investigated in comparison with a nonsteroidal antiinflammatory drug indomethacin. Stop-times i.e. the time elapsing from application, were determined for each drug. The rank order of potency at and lo-' M concentrations of the drugs was : nifedipine >verapa- mil 1 indomethacin. However, no significant difference of the stop-times was observed at M concentration of the drugs tested. The rhythmic contractions were re-activated by PGF2, after stoppage with indomethacin but not with nifedipine or verapamil. These results suggest that not only endogenous PG synthesis but also an influx of calcium from the extracellular space is respon- sible for the spontaneous rhythmic activity of human ureter. The beneficial effects of using calcium antagonists in the treatment of ureteric colic is discussed.

Key Words.: ureter, man, inhibition, calcium antagonists.

Introduction

Anticholinergic drugs are commonly used in the treatment of renal and ureteric colic because of their spasmolytic effect. In recent years, non-steroidal anti- inflammatory drugs (NSAIDs) have been used more frequently and this promoted the studies regarding their mechanism of action in isolated ureteral preparations from different species (HOLMLUND & SJODIN, 1978; LUNDSTAM ef al., 1982). It was concluded that in vifro rhythmic contractions of the ureter are dependent on endogenous prostaglandin synthesis since the cyclo- oxygenase inhibitors block these contractions (THULESIUS & ANGELO-KHATTAR, 1985; THULESIUS et al., 1986).

On the other hand, it was shown that KCI-induced contractions of guinea-pig isolated ureter was inhibited by nifedipine and verapamil and the involvement of an influx of Ca2+ through calcium channels sensitive to these calcium antagonists in this activity was suggested (MAGGI & MELI, 1984). Furthermore, in a few clinical trials, the beneficial effects of nifedipine in the treat- ment of renal and ureteric colics has also been reported (CARROL, 1985; BORTOLOTTI, 1987). Therefore, the pre- sent study was undertaken to determine if calcium an- tagonists, verapamil and nifedipine would alter the spontaneous rhythmic contractions of human isolated ureter like a NSAID indomethacin.

Materials and Methods

Human ureters were obtained from donor subjects (4 males, 7 females) undergoing kidney transplantation. Immediately after removal from the patient, the samples of ureter were immersed in ice-cold Krebs- Henseleit solution and transferred to the laboratory for in vitro testing. From the ureters, ring preparations of approximately 5 mm long were dissected out and mounted between L-shaped stainless steel wires in 10 ml organ baths filled with Krebs-Henseleit solution. The composition of the solution was (mM) : NaCl, 118.2; KC1,4.7; MgS04, 1.2; CaCl,, 2.5; KH2P04, 1.2; NaHCO,, 25; glucose, 11.1. The solution was main- tained at 37°C and bubbled with 95% 0, - 5% CO,. An initial resting tension of 1.5 g was applied to the tissues and the isometric contractions were displayed on a Gemini recorder (Model 7070) by means of a force- displacement transducer (Ugo Bade, 7004).

Only the ureteral preparations which showed spon- taneous rhythmic activity were used in this study. The rhythmic contractions usually started in about 45-60 min. After a stable pattern of rhythmic contractions was established, the drugs (nifedipine, verapamil or in- domethacin) at - M concentrations were add- ed to the bath and the effect on frequency and amplitude was observed. Also the stop-time i.e. the time to complete cessation of rhythmic contractions from

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246 A. SAHIN, I . ERDEMLI, M. BAKKALOGLU, A. ERGEN, I. BASAR AND D. REMZI

the time of drug addition, was determined for each drug. One concentration of a drug was tested in each preparation.

In some experiments, PGFzo, was administered after stoppage of activity in order to ascertain if con- tractions could again be elicited while the test drugs are still in the bathing fluid.

Control experiments were performed without ad- dition of test drugs to the organ bath to observe the change in rhythmic contractions over a period of 2 h.

Results are expressed as mean k S.E.M. of number (n) of experiments. Statistical comparisons were made by the use of Student’s t-test at the significance level of 0.05.

Results Human isolated ureteral ring preparations showed

spontaneous rhythmic motility. The ureteral contrac- tion can be described as a rapid rise in tension making a peak, followed by a quick relaxation and a subsequent short resting period. The mean values of frequency and amplitude of spontaneous rhythmic activity are 1 . 1 1 + 0.12 c/min and 3.12 + 0.14 g respectively (n = 36).

In the control experiments, the activity was ob- served over a period of 2 h without addition of the test drugs to the organ bath. The frequency and the amplitude of the spontaneous rhythmic contractions of isolated ureters did not change singificantly during this period.

The calcium antogonists (verapamil and nifedipine) and indomethacin did not alter the baseline tension of the preparations when added to the organ bath at - M concentration. The stop-time which is the time elapsing from the application of test drug to the com- plete inhibition of ureteral contraction was determined rather than frequency or the amplitude for each drug because the reduction in the amplitude and the frequen- cy of the ureteral contractions after addition of the drugs to the organ bath was not uniform and usually the motility stopped abruptly.

C ._ E

E

- a,

.- c

a 0

v) c

- L o g c o n c e n t r a t i o n (M)

FIG. 1 . - Log concentration - stop time relationship of nijedipine (< >). verapamil (A) and indomethacin (0) in human isolated ureteralpreparations. n =4 for each concentration of the drugs tested.

The relation of log concentration of the tested drugs and the stop-time is plotted in Figure 1. The concen- tration-response curves of verapamil and nifedipine seem to be parallel and were quite different from that

of indomethacin. Indomethacin exhibited a linear rela- tionship between the log concentration and the stop- time. At the highest concentration used M), the stop-times of all the drugs tested were within 10 min and were not significantly different. When the M and M concentrations were considered, nifedipine was found to have the shortest stop-time. The stop- times of verapamil and indomethacin at M con- centration were not significantly different. But at lo-’ M concentration, verapamil was found to be more po- tent than indomethacin.

In some experiments, the ureteral ring preparations were restimulated with PGFza after the cessation of rhythmic contractions with the test drugs. When in- domethacin at - M concentrations were used to inhibit the motility, addition of PGFb(10-7 M) promptly re-established contractions in a pattern which was similar in frequency and amplitude to that before application of indomethacin (Fig. 2A). This effect of PGFzo, - M) cumulatively did not further in- crease the frequency or the amplitude of contractions. However, after the stoppage of rhythmic contractions with verapamil or nifedipine - M), PGF,, usually failed to re-activate the contractions but only in some preparations induced only a train of contrac- tion of 2 to 8 bursts at or M concentrations and then the preparation stayed quiescent (Fig. 2B).

Discussion In the present study, the cyclooxygenase inhibitor

indomethacin concentration-dependently inhibited the spontaneous rhythmic activity of human isolated ureter obtained from donor subjects undergoing kidney transplantation. This confirms the previous studies which suggest that PGs play a role in controlling ureteral motility (THULESIUS et af., 1986; AL-UGAILY et af., 1986). The beneficial effects of NSAIDs like in- domethacin in the treatment of renal and ureteric co- lic has been attributed to their inhibitory effect on en- dogenous PG synthesis in the kidney which results in a decrease in urine volume and a decrease in renal or ureteral pressure (HOLMLUND & SJODIN, 1978). But the possible effects of NSAIDs on the ureter was also con- sidered since cyclooxygenase inhibitors block the ureteral rhythmic contractions (THULESIUS et al., 1986).

It was also shown that calcium antagonists inhibited the KC1-induced rhythmic contractions in guinea-pig isolated ureter (MAGGI & MELI, 1984). The contractions of human isolated ureter which were triggered by high K-concentrations were also highly sensitive to calcium antagonists (HERTLE & NAWRATH, 1984). Moreover, in a few clinical trials, it has been reported that nifedipine was effective in the treatment of renal and ureteric colic by a spasmolytic activity (CARROL, 1985; BORTOLOTTI et af., 1987).

Our results show that the calcium antagonists nifedipine and verapamil inhibit the spontaneous rhythmic contractions of human isolated ureter and this effect was comparable to that of indomethacin. At the highest concentration used M), all the test drugs stopped the rhythmic contraction within 10 min. However, with lower concentrations and M), differences in the stop-times were observed. The rank

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CALCIUM ANTAGONISTS AND HUMAN ISOLATED URETER 247

A

B .

I I N D O M E T H A C I N

T w I N l F E D l P l N E

PG F20c

PG F20(

FIG. 2. - Sponianeous rhythmic contractions of human isolated ureieral rings before and after addition of indomethacin, A (a1 arrow, I O F M) and nifedipine, B (at arrow, 10.’ M). The preparations were re-stimulated with PGF,, after cessation of rhythmic contractions with the test drugs. The concentrations of PGF, were lo-’ M at A and M at B.

order of potency of the tested drugs at these concentra- tions was estimated as follows : nifedipine > verapa- mil I indomethacin.

When the log concentration-stop time curves were analyzed the difference between the test drugs of both mechanism of action was apparent. Previously, it has been reported that increasing concentrations - M) of NSAIDs including indomethacin and their stop-times ex- hibited linear relationship in sheep ureter in vitro (BHARGAVA & THULESIUS, 1987). The same linearity of the concentration-response curve of indomethacin in human isolated ureter was also obtained in the present study. When the calcium antagonists were used to inhibit the rhythmic contractions, the log concentration-stop-time curves of both verapamil and nifedipine were parallel and unlike indomethacin, they did not exhibit any linearity.

The most striking finding of the present study is the re-establishment of rhythmic contractions with PGF,, after stoppage with indomethacin but not with the calcium antagonists nifedipine and verpamil. It has been propo- sed that the role of stimulatory PGs on ureteral rhythmic contractility is an all or non reaction; a certain level of PG-induced stimulation is necessary for the spread of ureteral contractions (THULESIUS et al., 1987). However, in the present study, inhibition of spontaneous rhythmic contractions of human isolated ureter with nifedipine or verapamil and failure of PGF,, to re-activate it suggest that an influx of Caz+ through calcium channels is also responsible for this motility.

Ureteral motility has been studied to a wide extend in various species. There are only few in vitro studies related to the human ureter and these were obtained from patients undergoing nephrectomy for various kidney diseases (mainly bilharzial nephropathy and malignancy) (HERTLE & NAWRATH, 1984; ANGELO-KHATTAR et al., 1985). However, in the present experiments the specimen were

obtained from the donor subjects undergoing kidney transplantation so that the experiments were performed in normal human isolated ureters, which underlines the importance of the data obtained from this study.

In conclusion, our results suggest that both PGs and extracellular Ca2+ are essential for the triggering and the maintenance of the spontaneous rhythmic contractility in human isolated ureters. Moreover, the calcium antagonists were found to be more potent than the PG synthetase in- hibitor indomethacin in inhibiting this activity. Therefore, besides confirming the previous clinical studies, it is reasonable to anticipate that in the treatment of ureteric colic, a calcium antagonist such as nifedipine might have more beneficial effects or when NSAIDs fail to relieve pain or produce undesirable side effects, calcium antagonists could be chosen as an alternative drug.

References AL-UCAILY, L., THULESNS, 0. & ANCELO-KHATTAR, M. (1986) Scand.

J. Urol. Nephrol. 20, 225-229. ANCELO-KHATTAR, M., THULESIUS, O., NILSSON, T., CHERIAN, T. &

JOSEPH, L. (1985) Scand. J. Urol. Nephrol. 19, 261-265. BHARCAVA, K.P. & THULESIUS, 0. (1987) Gen. Phormac. 18, 337-340. BORTOLOTTI, M., TRISOLINO, G. & BARBARA, L. (1987) JAMA 258,3516. CARROL, W. (1985) Ann. h i . Med. 102, 864. HERTLE, L. & NAWRATH, H. (1984) J. Urol. 132, 1265.1269. HOLMLUND, D. & SJODIN, J . (1978) J. Urol. 120, 676-677. LUNDSTAM, S.O.A., LEISSNER, K.H., WAHLANDER, L.A. & GRAL, J.G.

MAGGI, C.A. & MELI, A. (1984) Experieniia 40, 681-686. THULESIUS, 0. & ANGELO-KHATTAR, M. (1985) Acta Pharmacol. Toxi-

THULESIUS, O., UGAILY-THULESIUS, L. & ANGELO-KHATTAR, M. ( I 986)

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Prof. ERDEMLI Department of Pharmacology, School of Medicine, Hacetteppe University Ankara, Tiirkiye

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