Effects of diltiazem on renovascular-hypertensive and on normotensive rats

Vol 13 pp 165 to 168 1982 Printed m Great Bntam All rights reserved

0306-3623/82/020165-0450300/0 Copyright © 1982 Pergamon Press Ltd

Gen Pharmat

EFFECTS OF DILTIAZEM ON RENOVASCULAR-HYPERTENSIVE AND ON NORMOTENSIVE RATS P THII~VANT, J BARANES, M LE HEGARAT, F CLOSTRE and F V DEFEUDIS* D6partment de Pharmacologie, lnsutut Henri Beaufour, 72 Avenue des Troplques, 91940 Les Uhs, France

(Received 3 August 1981) Abstract--I The effects of 10-mm perfuslons of dduazem (0 1-2 5 mg/kg, i v ) on arterial blood pressure were stu&ed in anaesthetized renovascular-hypertenslve and m normotensive rats 2 Ddtiazem produced a dose-dependent decrease m blood pressure m hypertensive rats (EDso - 1 mg/kg) 3 Ddtiazem also decreased blood pressure in normotenslve rats, but this action was less sustained than in hypertensive rats 4 These results support the contention that ddtiazem might be useful for treating arterial hypertension

water ad hbltum The animals were anaesthetized m the morning with ethyl carbamate (Prolabo, 1 25 g/kg, I p, admlmstered m a volume of 10ml/kg body weight), ethyl carbamate was dissolved in 09~o NaC1, and at the dose employed it induced anaesthesia lasting throughout the experiment (about 7 hr) After a laparotomy, the renal peduncles were freed, the right peduncle was hgatured and the left one was clamped for five hours The right carotid artery of each animal was catheterized and connected to a transducer (Narco, Type RP-1500) Mean arterial blood pressure was recorded using a, physlograph (Narco) The right jugular vein was also catheterized and connected to a perfusor (Braun, Type Perfusor I), the catheter and syringe unit being filled with the solution to be administered Thirty minutes before declamping the left renal peduncle the rats were rejected with atropme-SO,, (Prolabo, Pans, France, 1 mg/kg in a volume of 1 ml 0 9% NaCl/kg body weight) m the vein of the penis to ehmmate any parasympathetic influence Six rats, divided into three groups of two rats, were studled each day, normotenswe control rats (operated controls), hypertenswe control rats, hypertensive rats which recewed a given dose of dlltlazem (L E R S, Paris, France) As hypertension developed immedmtely after declampmg, intravenous perfusion of ddtlazem (0 1-2 5 mg/kg, dissolved in 0 9~o NaCI) was begun simultaneously with the declamplng procedure and was continued for 10 minutes at a rate of 0 l ml/mm Untreated normotenswe and hypertensive rats were perfused with an equivalent volume of 09~o NaCI Mean arterial blood pressure was recorded for 90 mm after the start of perfuslon Results are expressed as means + SEM, Student's t-test was used to compare the blood pressure of hypertensive controls with that of normotenswe controls, and the blood pressure of hypertensive dlltlazem-treated rats with that of hypertenswe controls, at various times after initiating perfusion

INTRODUCTION

During the past few years calcium-antagonists (slow channel blocking agents) have come to play a very important role m the therapy of angina pectorts, but apart from their anU-anglnal effect, they also appear to be useful for treating arterial hypertension, attacks of acute hypertension, obstructive cardlomyopathles, supraventncular arrhythmlas, arterms, and Raynaud's syndrome (e g Wellens et al, 1977, Slngh et al, 1978, Rahwan et al, 1979, Henry, 1979, 1980, Aokt et al, 1979, Mtdtbo & Hals, 1980, Llchtlen et al, 1980) K l y o m o t o (1979) demonstrated an antlhypertenslve effect of dlltlazem in a model of chronic renal hypertension in the rat ("Goldblatt one-ktdney" model, consisting of partial constrlcUon of the left renal artery, followed by ablation of the right kidney one week later) Dtltmzem was studied 4-6 weeks after nephrectomy when the systohc blood pressure of the ammals had reached 210-240mm Hg The hypertension which developed was not renln-dependent In this study, Uiltmzem also produced an hypotenslve effect on conscious, anaesthetized normotenslve rats (see also Cavero et al, 1979) The present report shows the effects of dlltlazem obtained with a model of acute renln-dependent hypertension which has already been described (Engel et al, 1973, see also Taqulnl, 1940) The action of dlltmzem on anaesthetized normotens~ve rats has also been re-examined MATERIALS

AND

METHODS

Preparation of hypertenslte rats Male Sprague-Dawley rats, about 12 weeks old and weighing 250-280 g, were used They were given food and

Preparation of normotenswe rats Different doses of ddtiazem were also studied using atropine-treated, anaesthetized normotensive rats under the same experimental conditions except that the laparotomy was not performed in these experiments

* Present address Director of Biology, U P S A, 128 Rue Danton, B P 325, 92506 Rued-Malmalson Cedex, France op 132-G

165

166

P THIEVANTet al 180 170

160"

DILTIAZEM

-IE 1so E

~pertens,ve

140

~, ~ 130

/9.-.

® ~.~ 120

,~.. 0.1 m g / k g

~ • -_~ - . - 9-- - - o - -. - 6 - - - c. , "

,,

.......

&

-

0.5 mg/kg

110

100

o

<

;," 2 . 5 m g / k g

90

80 ~er|usloA 70 0

3 5

10

15

20

25

30

40

50

Time,

60

35

90

m,nutes

F;g t Dose-response effect of a i0-mm intravenous perfus]on of diltmzem ]n renovascular-hypertens]ve rats St]ppled areas m&cate control values (means _ SEM) for normotens]ve 01 = 8) and hypertenstve (n = 6) rats Mean values are plotted for results obtained with all doses of ddtmzem (5 or 6 rats m all cases] SEM varied between 2-14°o, *indicates that these values differed slgmficantly (P < 0 0 5 - P < 0 0 0 1 ) from corresponding control values for hypertensive rats (Student's t-test two-tailed) RESULTS

Actton o f <~azem m hypertenstte rats Hypertension Induced by declamplng the left renal peduncle was maximal after a b o u t five minutes (mean artertal blood pressure = 169 _+ 7 5 m m Hg, mean +__ SEM of 8 values) and rema,ned significantly elevated with respect to n o r m o t e n s w e controls for at least 90 m m after declampmg (F,g l) All doses of ddttazem-studted produced sigmficant decreases in blood pressure Dose-dependenc) o f the actzon o f dl/t,azem on hApertenSlbe r a t s

A dose-dependent antlhypertenswe effect of dtltmzem was observed at all times studted from 5-30 m m (Fig 2) The m a x i m u m difference between the blood pressure of hypertensive ammals a n d dtltmzemtreated hypertenswe ammals occurred 5 m m after declamping EDsos for the &fference between maximal hypertenswe response of control ammals and maximal hyper- or hypotenstve response of drug-treated animals ranged from a b o u t 0 7 mg/kg after 5 m m to a b o u t 1 3 mg/kg after 30rain Action o f dtlt~azem on normotenst~e ~ats The highest dose of ddtlazem stu&ed (2 5 mg/kg) produced ~ts maximal hypotensxve effect on normotenswe rats during the first 10 mln, but this act,on was less sustained than m hypertensive rats (Ftg 3) DISCUSSION

In an acute model of renovascular hypertension,

intravenously-perfused ddtlazem produced a dosedependent antlhypertenstve effect "Fhe dose reqmred to prevent the mcrease m blood pressure due to removal of the clamp on the left renal peduncle was a b o u t 1 mg/kg After 1 0 m m (corresponding to the end of dtltlazem perfuston) m hypertensive rats arterial blood pressure was decreased by 40 m m Hg with 0 5 mg/kg daltlazem, by 56 m m Hg with 1 mg/kg dxltlazem and by 82 m m Hg with 2 5 mg/kg ddttazem Klyomoto (1979) also observed a dose-dependent ant,hypertensive effect of dtltmzem, i e a decrease m arterial pressure of 40 m m Hg wtth an acute intravenous in lectlon of 0 1 mg/kg of ddttazem, and a decrease of 6 5 r a m Hg w~th 0 3 m g / k g of ddtmzem Therefore the results presented here are not very different from those reported by Klyomoto (1979), even though the experimental con&t~ons were not the same, m his study a chromc model of hypertension was used and ddttazem was admlmstered by acute intravenous injection Also, in accord with the present results, Klyomoto (1979) demonstrated that dllttazem produced a dose-dependent hypotens,ve effect m urethane-anaesthettzed normotenslve rats and that this effect was less pronounced than m hypertenswe rats Furthermore, Ishn and co-workers (1980) showed that nffedlpme produced dose-dependent decreases in arterial blood pressure both in spontaneously-hypertenstve rats and In rats w~th D O C A Induced hypertension or renal hypertension, and that nifedIpine produced more pronounced blood pressure decreases m hypertenstve than in normotens~ve ammals Regarding the mechanism of action of dllttazem,

Diltiazem and hypertension 90

hypertension produced by intravenously-rejected angiotensln-II, and Cavero et al (1979) observed inhibition by dlltlazem of pressor responses to intravenous norepmephrine or spinal cord stimulation in pithed rats The results presented hereto provide further support for these contentions

5 Iqnln e

DILTIAZEM

//i~

"I-

lOm,n

r,

//

E E =-

167

REFERENCES /I/'

[~] 15mm

// s

'

,'

AOK1 K , KONDO S, MOCHIZUKI A , SATO K , YOSHIOA T,

I

vl t It

L_ ~

30ram

5O.

¢°~ . . - - ~ 141

e, e: lo

Log

dose, mg/kg

i.v.

Fig 2 Dose-response curves for the effect of ddtiazem on renovascular-hypertensive rats at various times after declampmg and initiating intravenous perfusion of diltiazem These curves were constructed by plotting the differences between arterial blood pressure of "'control hypertensive" and dlltlazem-treated hypertensive rats (see Fig 1) Klyomoto (1979) and Ishll and colleagues (1980) suggested that it might produce a vasoddation of the renal and peripheral arteries, leading to a decrease m peripheral resistance Klyomoto (1979) also observed a non-competitive inhibitory effect of ddtiazem on

KATO S & KATO K (1979) CaZ+-antagonist therapy for hypertension in combination with beta-blockade A new concept of essential hypertension Perspect Cardtovas~ Res 4, 377-386 CAVEROI, BOUDOTJ P, LEFEVRE-BORGF & ROACH A G (1979) Pharmacological evaluation of d]ltlazem and its desacetylated metabohte in several animal species In New Drug Therapy with a Calcium Antaoon#~t--Diltiazero Hakone Sympostura 1978, pp 61-88 Excerpta Medica, Amsterdam ENGEL S L, SCHAEFFER T R, WAUGH M H & RUBIN B (1973) Effects of the nonapeptide SQ 20881 on blood pressure of rats with experimental renovascular hypertension Proc Soc exp Biol Med 143, 483~,87 HENRY P D (1979) Calcium ion (Ca 2+) antagonists Mechanisms of action and clinical applications Practical Cardlol 5, 145-156 HENRY P D (1980) Comparative pharmacology of calcium antagomsts Nifedlpine, verapamil and diltiazem Am d Cardlol 46, 1047-1058 ISHII H, ITOH K & NOSE T (1980) Different antihypertensire effects of nifediplne in conscious experimental hypertensive and normotensive rats Eur J Pharmac 64, 21-29 KIYOMOTOA (1979) Antlhypertensive effects of diltiazem in rats In New Druo Therapy with a Calcium Antagonist-Diltiazem Hakone Symposium 1978, pp 112-125 Excerpta Medica Amsterdam LICHTLEN H, ENGELJ, WOLF R & AMENDE I (1980) The effect of the calcium antagonistic drug nlfedipine on coronary and left ventricular dynamics in patients with coronary heart disease In Calcium Antayonists (Edited by FLECKENSTEIN A & ROSKAMM H), pp 270-281 Springer Verlag, Heidelberg M]DTBO K & HALS O (1980) Verapamil m the treatment of hypertension Curr ther Res 27, 830-838 RAHWAN R G , PIASCIKM F & WIT1AK D T (1979) The role of calcium antagonism in the therapeutic action of drugs Can J Phystol Pharrnac 57, 443-460

m 1)0 -Je.

E it:: 120

. 110 o 100

m t& 9O m

•

~ io

8O

'~

79

•

Q

• B

perius,on

o

3

s

to

t5

2o

25

3o

4o

5o

so

7s

T,me.m,nutes

Fig 3 Dose-response effect of a 10-mln intravenous perfusion of diltiazem in normotensive rats The stippled area indicates control values (means + SEM, 5 rats) Mean values are plotted for results obtained with all doses of diltlazem (5 rats in all cases) SEM varied between 2-9%, * indicates that these values differed significantly (P < 0 01 or P < 0 001) from corresponding control values (Student's t-test, two-tailed)

90

168

P THII~VANTet al

SINGH B N, ELLRODTG & PETER C T (1978) Verapamd A review of its pharmacological properties and therapeutic use Dru~/s 15, 169-197 TAQUrNt A C (1940)The production of pressor substance by the totally lschemlc kidney Am Heart J 19. 513-518

WELLENS H J J. TAN S L, BAR F W H, DUREN D R, LIE K I & DOHMEN H M (1977) Effect of verapamll stu&ed by programmed electrical stimulation of the heart m patients with paroxysmal re-entrant tachycar&a Br Heart J 39, 1058-1066