Plasma Volume, Blood Volume and Transcapillary Escape Rate (TER) of Albumin in Young Spontaneously Hypertensive Rats (SHR) as Compared with Normotensive Controls (NCR)

We compared some of our latest experiments on blood pressure control and erythrocytosis in spontaneously hypertensive rats with Gaar's computer-simulated studies, which suggest that erythrocytosis is a key to understanding the hemodynamic changes in hypertension. We tested two of Gaar's several predictions: (i) peripheral vascular resistance decreases when the feedback control of erythrocytosis is blocked and (ii) in primary hypertension, blood volume is increased slightly. We also studied the interrelation of systolic blood pressure and plasma renin substrate in spontaneously hypertensive rats, and the effect of diet on renin, blood pressure, and erythrocytosis. Our data showed that (i) on a percentage basis the renin system supports blood pressure essentially in the same manner in normal and hypertensive rats, (ii) peripheral vascular resistance decreased when erythrocytosis was partially blocked by feeding a low-iron diet, (iii) blood volume was similar in normal and hypertensive rats, and (iv) dextrin stimulates plasma renin, packed cell volume, and blood pressure in hypertensive rats. We conclude that blood pressure and erythrocytosis are interrelated, that the combined data of simulated and experimental studies support the notion that primary hypertension is a blood-vessel adaptation in response to a renal energy need that may require additional oxygen.Key words: angiotensinogen, renin, dextrin, packed cell volume.

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Vasopressin and renin response to plasma volume loss in spontaneously hypertensive rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1986.250.3.h443 ◽

1986 ◽

Vol 250 (3) ◽

pp. H443-H452 ◽

Cited By ~ 4

Author(s):

C. D. Sladek ◽

M. L. Blair ◽

Y. H. Chen ◽

R. W. Rockhold

Keyword(s):

Plasma Volume ◽

Spontaneously Hypertensive Rats ◽

Renin Angiotensin System ◽

Hypertensive Rats ◽

Angiotensin System ◽

Spontaneously Hypertensive ◽

Renin Angiotensin ◽

Old Rats ◽

Wistar Kyoto ◽

Renin Content

Abnormalities in the vasopressin (VP) and renin-angiotensin systems have been described in spontaneously hypertensive rats (SHR). Responsiveness of these systems to a decrease in plasma volume was examined in the SHR at 6, 8, and 18 wk of age and compared with responses in age-matched normotensive Wistar and Wistar Kyoto rats (WKY). Trunk blood was collected 3 h after administration of 2 ml/100 g body wt of 0.9% saline, 15 or 30% polyethylene glycol (PEG), and in one group of conscious 8- and 18-wk-old rats, mean arterial pressure was monitored following PEG administration. Hematocrit and serum VP increased significantly in both strains at all ages following PEG. At 6 and 8 wk of age, the VP response to the PEG injection was significantly greater in SHR compared with WKY (P less than 0.005), but at 18 wk the response was comparable in the two strains. Serum renin activity (SRA) also increased in both strains receiving PEG at 6 and 8 wk of age, but the response was suppressed in the SHR relative to the WKY (P less than 0.001). At 18 wk of age, SRA increased in WKY, but the response was totally suppressed in SHR. Renal renin content in a separate group of rats was reduced in 19-wk-old SHR compared with WKY (P less than 0.001) but was not different in 5- and 8-wk-old rats. Thus there appears to be a hyperresponsiveness in the VP system in young SHRs that is not present in the renin-angiotensin system. The divergence in the responsiveness of the renin and VP systems and the attenuation of responsiveness in the VP system in 18-wk SHRs indicate a differential effect of the hypertensive process on the VP and renin systems in the SHR.

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Central Blood Volume in Spontaneously Hypertensive Rats and Wistar-Kyoto Normotensive Rats

Clinical Science ◽

10.1042/cs059389s ◽

1980 ◽

Vol 59 (s6) ◽

pp. 389s-391s ◽

Cited By ~ 6

Author(s):

S. Lundin ◽

B. Folkow ◽

P. Friberg ◽

B. Rippe

Keyword(s):

Blood Volume ◽

Spontaneously Hypertensive Rats ◽

Total Blood Volume ◽

Central Blood Volume ◽

Hypertensive Rats ◽

Total Blood ◽

Spontaneously Hypertensive ◽

Structural Wall ◽

Wistar Kyoto Rats ◽

Wistar Kyoto

1. Central blood volume and total blood volume were determined in spontaneously hypertensive rats and Wistar-Kyoto rats at two ages (6 and 12 weeks), representing ‘borderline’ hypertension and early ‘established’ hypertension. 2. A technique was used where plasma and erythrocyte indicators were injected into conscious rats. Blood volume in the cardiopulmonary compartment, present in the ‘resting’ awake steady state, could then be estimated by sudden freezing of the entire rat. 3. Twelve week-old spontaneously hypertensive rats showed a decreased total blood volume, and the fraction of blood contained in the cardiopulmonary area was significantly increased compared with that of normotensive Wistar-Kyoto rats. 4. In 6 week-old spontaneously hypertensive rats, total blood volume was only marginally decreased but here also a tendency towards centralization of the blood was seen. 5. Thus, along with the development of spontaneously hypertensive rat hypertension, a decreasing blood volume tends to become increasingly centralized to the cardiopulmonary area. Both neuro-hormonal influences and structural wall changes in the low-pressure capacitance side may contribute to this.

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