The cardiovascular effects of vasopressin after haemorrhage in anaesthetized rats.

Abstract

SUMMARY1. The cardiovascular effects of an acute haemorrhage (2 % of the body weight)were studied over a 60 min period in three groups of rats: (a) Brattleboro rats with hereditary hypothalamic diabetes insipidus (b.d.i.) lacking circulating vasopressin, (b) control rats of the parent Long Evans (l.e.) strain, and (c) l.e. rats treated with an antagonist of the vascular action of vasopressin.2. Prior to the haemorrhage there were no significant differences between the three groups of rats with respect to mean arterial blood pressure, cardiac output, stroke volume or total peripheral resistance.3. Following the haemorrhage cardiac output and stroke volume were severely reduced in all three groups of rats. Total peripheral resistance was relatively unaffected in antagonist-treated l.e. rats and b.d.i. rats, but rose substantially in response to the loss of blood in the control l.e. group. Both total peripheral resistance and mean arterial blood pressure were markedly greater in the untreated l.e. control rats than in the other two groups of animals during the first 20 min after haemorrhage.4. The mean heart rate measured in Brattleboro rats was elevated compared with that of control l.e. rats throughout the experiment and, in addition, significantly greater than that of antagonist-treated l.e. rats during the first 40 min after the haemorrhage.5. Survival rate for the b.d.i. rats following the 2 % haemorrhage was lower than that for l.e. control rats and antagonist-treated l.e. rats.6. The results indicate that the recovery of the blood pressure following an acute arterial haemorrhage is significantly influenced by vasopressin, particularly during the first 20 min, and that the predominant effect of the hormone is to increase the total peripheral resistance. The higher mortality associated with volume depletion in the b.d.i. rats is unlikely to be directly related to the absence of the vascular action of vasopressin, since administration of the vasopressin antagonist to normal l.e. rats does not reduce their survival rate.

The renal vascular response to mild and severe haemorrhage in the anaesthetized rat.

“…It is also established that microspheres provide an accurate measurement of total renal blood flow (Tsuchiya, Ferrone, Walsh & Frohlich, 1978;Mimran & Casellas, 1979). Although doubts have been expressed over the suitability of microspheres for measuring the distribution of flow within the kidney, owing to the possibility of axial streaming in the interlobular arteries (see Ofstad & Aukland, 1985), streaming can be minimized by the use of 10 psm spheres, as in the present study, rather than the standard 15 ,um spheres (Sabto, Bankir & Griinfeld, 1978); in the rat the entrapment of the smaller spheres in glomeruli is virtually complete (see Al-Omar Azzawi & Shirley, 1983 (Siren et al 1986) and Inactin-anaesthetized (Chapman, Hreash, Laycock & Walter, 1986) rats after severe haemorrhage.…”

Cardiovascular interactions between vasopressin, angiotensin and noradrenaline in the Brattleboro rat

“…The effect of haemorrhage on blood pressure and its subsequent recovery confirmed that Brattleboro rats are more sensitive to blood volume depletion Johnston et al, 1981;Chapman et al, 1986) and that destruction of peripheral sympathetic nerve endings has a more profound effect on the pressor response to haemorrhage in these animals than in the control Long Evans rats. Pretreatment with 6-hydroxydopamine did appear to be associated with a greater susceptibility to the hypotensive effect of haemorrhage in both strains but the depressor effect was significantly more marked in the Brattleboro DI rats.…”

“…Then all rats were anaesthetized with Inactin (I20mgkg-, i.p.) and surgically prepared as described elsewhere (Chapman et al, 1986). Briefly, cannulae were inserted into the bladder, a femoral artery for measurement of heart rate and arterial blood pressure and a femoral vein for infusion of 150 mmolI' NaCl at a rate of 0.5ml 100g-1h1 (and, via an additional cannula in the BDI rats only, 2% glucose solution at a rate determined from the urinary excretion rate to maintain fluid balance).…”

Vasopressin V1‐receptor Blockade Lowers Arterial Blood Pressure in Young Conscious Long‐evans Rats

“…The neurohypophysial hormone vasopressin has been shown to be important in maintaining arterial blood pressure in specific situations such as haemorrhage (see, for example, Chapman, Hreash, Laycock & Walter, 1986) and water deprivation (see, for example, Andrews & Brenner, 1981). Adult Brattleboro rats with hereditary diabetes insipidus (BDI), lacking circulating vasopressin, and rats of the parent Long-Evans (LE) strain have similar basal arterial pressures whether anaesthetized (Chapman et al 1986) or conscious (Gardiner & Bennett, 1985).…”

“…Adult Brattleboro rats with hereditary diabetes insipidus (BDI), lacking circulating vasopressin, and rats of the parent Long-Evans (LE) strain have similar basal arterial pressures whether anaesthetized (Chapman et al 1986) or conscious (Gardiner & Bennett, 1985). However we have reported recently that young BDI rats, both anaesthetized and conscious, have a lower mean arterial pressure than age-matched control LE rats (Laycock & Obika, 1988).…”