Vascular and cardiac effects of HP 406 and nifedipine in vitro and in conscious spontaneously hypertensive rats and renal hypertensive dogs

Calcium absorption by spontaneously hypertensive rats (SHR) was variably reported to be different from normotensive Wistar-Kyoto (WKY) controls. Furthermore, blunted responsiveness to the intestinal effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] has also been postulated. To evaluate this hypothesis, calcium fluxes were measured by the Ussing technique across duodenum and descending colon with or without prior 1,25(OH)2D3 treatment. Duodenal mucosal-to-serosal calcium flux (Jm----s) (44.9 vs. 52.4 nmol X cm-2 X h-1), serosal-to-mucosal flux (Js----m) (25.6 vs. 28.4 nmol X cm-2 X h-1), and net flux (Jnet) were comparable. 1,25(OH)2D3 increased duodenal Jm----s in both SHR and WKY groups (95.2 and 86.8 nmol X cm-2 X h-1). Js----m was lower in SHR (26.1 vs. 35.6 nmol X cm-2 X h-1, P less than 0.01), although the tendency for a higher Jnet in SHR (68.6 vs. 51.2 nmoles X cm-2 X h-1) was statistically insignificant. Short-circuit current was higher in the colon of SHR, both before and after 1,25(OH)2D3, suggesting increased sodium transport. Basal colonic Jnet was virtually zero in both groups but comparably increased by 1,25(OH)2D3 because of stimulation in only Jm----s. Prevention of hypertension by hydralazine since the 4th wk of age did not alter the findings compared with the hypertensive SHR, suggesting calcium transport rates were unaffected by hypertension. These data indicate that in vitro, duodenal, and colonic active calcium transport by the SHR is similar to WKY. Their normal responses to 1,25(OH)2D3 do not support the hypothesis of intestinal resistance.

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Myogenic tone in mesenteric arteries from spontaneously hypertensive rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1996.270.1.h1 ◽

1996 ◽

Vol 270 (1) ◽

pp. H1-H6 ◽

Cited By ~ 22

Author(s):

A. S. Izzard ◽

S. J. Bund ◽

A. M. Heagerty

Keyword(s):

Spontaneously Hypertensive Rats ◽

Mesenteric Arteries ◽

Myogenic Tone ◽

Hypertensive Rats ◽

Tension Development ◽

Spontaneously Hypertensive ◽

Wide Pressure Range ◽

Wistar Kyoto ◽

Wide Pressure

To investigate myogenic tone during the developmental and established phases of hypertension, segments of distal (6th order) mesenteric arteries from spontaneously hypertensive rats (SHR) at 5 and 20 wk were isolated and pressurized in vitro and compared with vessels from age-matched Wistar-Kyoto (WKY) control animals. At 5 wk, tone was significantly enhanced in the SHR. At 20 wk tone was no longer significantly increased over a wide pressure range, although arteries from the SHR were able to maintain diameter at all pressures studied, whereas vessels from the WKY exhibited forced distension at 180 and 200 mmHg. From the relative slope of the pressure-diameter relationship (myogenic index), no increase in peak myogenic responsiveness was observed in arteries from the SHR at either time point. Passive lumen diameters were significantly decreased in arteries from SHR at both time points. From the total and passive midwall circumference-tension relationships, total tension was observed at a reduced midwall circumference in the SHR, but increased absolute levels of total tension were not observed. The normalized midwall circumference-tension relationships in the two strains revealed increased total tension due to active tension development at a reduced normalized circumference at 5 wk in the SHR. At 20 wk the normalized midwall circumference-tension relationships in the two strains were identical. These results demonstrate that myogenic tone in mesenteric arteries is enhanced during the development of hypertension but not when it is established, except at high intraluminal pressures.

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MAPPING OF ANGIOTENSIN II RECEPTOR SUBTYPES IN PERIPHERAL TISSUES OF SPONTANEOUSLY HYPERTENSIVE RATS BY IN VITRO AUTORADIOGRAPHY

Clinical and Experimental Pharmacology and Physiology ◽

10.1111/j.1440-1681.1995.tb02868.x ◽

1995 ◽

Vol 22 (s1) ◽

pp. S17-S19 ◽

Cited By ~ 8

Author(s):

Keifu Song ◽

Yoshiko Kurobe ◽

Hironori Kanehara ◽

Takeo Wada ◽

Yoshiyuki Inada ◽

...

Keyword(s):

Angiotensin Ii ◽

Spontaneously Hypertensive Rats ◽

Receptor Subtypes ◽

Angiotensin Ii Receptor ◽

Hypertensive Rats ◽

Peripheral Tissues ◽

Spontaneously Hypertensive ◽

In Vitro Autoradiography ◽

Angiotensin Ii Receptor Subtypes

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Altered in vitro uptake of norepinephrine by cardiovascular tissues of spontaneously hypertensive rats. Part 1. Mesenteric artery.

Hypertension ◽

10.1161/01.hyp.3.6.704 ◽

1981 ◽

Vol 3 (6) ◽

pp. 704-709 ◽

Cited By ~ 13

Author(s):

J H Rho ◽

B Newman ◽

N Alexander

Keyword(s):

Mesenteric Artery ◽

Spontaneously Hypertensive Rats ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Cardiovascular Tissues ◽

In Vitro Uptake

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An antihypertensive extract of erythrocytes: effects on 45Ca uptake and efflux

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y86-068 ◽

1986 ◽

Vol 64 (4) ◽

pp. 424-429

Author(s):

G. L. Wright ◽

G. O. Rankin ◽

W. D. McCumbee

Keyword(s):

Blood Pressure ◽

Spontaneously Hypertensive Rats ◽

Calcium Uptake ◽

Slow Component ◽

Present Report ◽

Calcium Stores ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Washout Curves

The present report describes some aspects of the effects of a recently described antihypertensive extract of erythrocytes (AHF) on calcium uptake and efflux in rat aortae. AHF was found to be present in the erythrocytes of both spontaneously hypertensive rats and normotensive rats. Furthermore, AHF obtained from erythrocytes of SH rats was shown to be equally effective in suppressing lanthanum-resistant calcium uptake in aortae from hypertensive and normotensive rats. AHF treatment prior to incubation of aortae with 45Ca caused an apparent increase in the total 45Ca uptake. The analysis of calcium washout curves obtained for tissue in calcium-free or lanthanum-containing media indicated that AHF had no significant effect on the rate of calcium loss from the slow component of efflux, though this compartment tended to be reduced in size. This indicated that the increase in the 45Ca content of AHF-exposed aortae prior to rinsing was confined to the rapid component of efflux. The loss of calcium from the rapidly exchanging compartment was enhanced in either of the efflux media used. The results suggest that a principal action of AHF involves an increase in the lability and exchangeability of calcium stores. In addition to its effects in resting tissue, AHF abolished the increase in lanthanum-resistant calcium uptake induced in rat aortae by the addition of high K+ or norepinephrine to the incubation media. In a second part of the study, the effect of AHF on blood pressure and in vitro calcium uptake were compared with that of phosphatidylethanolamine (PEA), the probable identity of another endogenous antihypertensive (renin preinhibitor) compound earlier shown to share important functional similarities with AHF. The results reduce the likelihood that the two causal agents are identical. The AHF produced a significant (75 Torr, 1 Torr = 133.32 Pa) fall in the systolic blood pressure (SBP) of spontaneously hypertensive rats within 24 h following injection, whereas PEA had no effect on the SBP in this model. Both AHF and PEA reduced the resting in vitro uptake of "lanthanum-resistant" calcium in rat aortic segments. However, the AHF effect was significantly greater than PEA at each concentration studied.

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