Regional blood flow in conscious spontaneously hypertensive rats.

Abstract

In spontaneously hypertensive and normal control rats in the conscious state, blood flow was observed in the carotid artery, superior mesenteric artery, renal artery, and terminal aorta with a chronically implanted electromagnetic flow probe. At rest, flow per body weight was not different between the two groups except at the terminal aorta where it was significantly smaller in hypertensive rats (P<0.05).Regional peripheral resistance was higher in hypertensive rats than in normal rats in all the four arteries, but its elevation in the former was not uniform but most marked in the hindquarter area supplied by the terminal aorta. Quantitatively, this area was estimated to contribute about 40% of the total conductance decrease in hypertensive rats in comparison with the control. This suggests the importance of elevation of resistance in muscle blood vessels in hypertension. The contributions from the superior mesenteric area and the bilateral kidneys were estimated to be about 15 % each. In the transposition response induced by transposing rats from their home cage to a new cage, the increase in hindquarter flow was significantly greater in hypertensive rats than in normal rats (P<0.01).The sum of the mean flows of the four arteries, a measure of cardiac output, was not different between hypertensive and normal rats at rest but greater in the former during transposition response. Elevation of arterial pressure in the response in hypertensive rats but not in the normal rats was ascribable largely to a greater increase in cardiac output in the former than the latter.

Possible Involvement of Androgen in Increased Norepinephrine Synthesis in Blood Vessels of Spontaneously Hypertensive Rats

“…The NE levels and the TH activities in the abdominal aor ta and the mesenteric artery of SHR were significantly higher than those of WKY. Iriuchijima (6) reported that the elevation of the SHR's vascular resistance is not uniformly observed over the whole body, and it is especial ly marked in the abdominal aorta and the mesenteric ar tery. The vascular resistance of these arteries of SHR was about 50% greater than that of normotensive rats (18).…”

“…Judy et al (5) reported that sympathetic nerve activity is increased in the nerves distributing to the abdominal regions in SHR. Iriuchijima (6) reported that the high vascular resistance in hindquarter and mesenteric arteries of SHR is maintained by an elevated sympathetic tone. Therefore, increased sympathetic tone or sympa thetic nerve activity in arteries of these regions may con tribute to hypertension in SHR.…”

Regional difference in sympathetic vasoconstrictor tone in conscious rats.

“…This result suggests that, in the conscious state, sympathetic vasoconstrictor tone in resistance vessels of the hindquarter area is immaterial in normal rats in contrast to spontaneously hypertensive rats, in which hindquarter vasoconstrictor tone is important to their hypertension (IRIUcHIJIMA, 1983a).…”

Hemodynamic characteristics of conscious deoxycorticosterone acetate hypertensive rats.

“…It has been demonstrated by this method that, in spontaneously hypertensive rats (SHR, OKAMOTO and AOKI, 1963) and one-clip, two-kidney renovascular hypertensive rats, elevation of peripheral vascular resistance is not uniform over the entire body. In SHR, elevation of resistance is especially marked in the hindquarters (IRIUCHIJIMA, 1983). In one-clip, two-kidney rats, the area with marked resistance elevation is the splanchnic bed supplied by the superior mesenteric artery (TERANISHI and IRIUCHIJIMA, 1985).…”