Role of Arginine Vasopressin in Blood Pressure Control in Young Rats

Abstract

SummaryWe investigated the importance of arginine-vasopressin (AVP) for blood pressure control in young and adult rats. Most of the studies were performed on Brattleboro rats with complete diabetes insipidus (DI). In some protocols, Sprague-Dawley rats (SD) were also used. The rats were age 20-24 days (young) or 50-80 days (adult). Adult DI rats have a significantly higher mean arterial pressure (MAP) than adult SD rats. The studies were performed during normovolemia and hypovolemia. Hypovolemia was created by the rapid withdrawal of blood, 0.5-1.5% of body weight. Following bleeding 0.5% of the body weight, young DI rats had a significantly larger decrease in MAP than adult DI and young and adult SD rats. Continuous infusion of AVP (2000 pg ·100 g-l min-I) blunted the hemorrhagic hypotension in the DI rats.In all groups of rats studied, AVP had little effect on the MAP during normovolemia. The effect of AVP (given in a bolus dose of20 or 2000 pg.l00 g-l) on the MAP was in DI rats significantly related to the MAP immediately prior to the AVP administration. No effect on MAP was observed when the initial MAP was 105-112 mm in the young DI rats and 148-157 mmin the adult DI rats. The effect of AVP (20 pg·100 g-l) appeared to be submaximal to maximal. In anaesthetized SD rats, the basal AVP production was higher in the young than in the adult animals. Following bleeding, serum AVP increased in both young and adult rats but the increase was significant only in the adult rats.Abbreviations AVP, arginine vasopressin DI, diabetes insipidus BW, body weight SD, Sprague-Dawley MAP, mean arterial pressure Several investigators have reported that the serum levels of AVP are high in the perinatal period (9, 10). Pohjavuori and Fyhrquist (9) found that the AVP levels in serum from cord blood could be 100 times higher than in serum from the mother.It is generally recognized that AVP may have both an antidiuretic (14) and a hemodynamic effect (3,6,10). It is also well documented that the response to the antidiuretic effect is not fully developed at birth (12, 13). Newborn infants given high doses of DDAVP intranasally continue to produce an almost isotonic urine (15). Studies on isolated collecting tubules from rabbits have shown that the maximal increase in cAMP following exposure to AVP is significantly less in immature than in mature collecting tubules (13). Pohjavuori and Fyhrquist (9) therefore suggested that the high AVP production in the perinatal period was of importance primarily for blood pressure control.The vascular effects of AVP are less well investigated than the antidiuretic effects. The doses of AVP generally required to elicit significant changes in blood pressure are often 100 to 1000 times higher than the doses required to produce antidiuretic effects. The fact that hemorrhage is a potent stimulus for AVP release (4, 5) suggests that AVP is important for the prevention of hemorrhagic hypotension.The aim of this study was to evaluate the role of AVP for blood pressure control in hemorrhagic hypotension in y...

Use of Experimental Models to Study the Development of Renal Function

“…During hypovolemia AVP is of great importance for the maintenance of the arterial blood pres sure. The effect of AVP on the arterial pres sure during hypovolemia is at least as pro nounced in infant as in adult rats [11]. We have therefore suggested that the high AVP levels in the perinatal period are of major importance for the control of blood pressure and regional blood flow and of minor impor tance for water balance.…”

Ovine Fetal Response to Water Deprivation: Aspects on the Role of Vasopressin

“…A potent vasoconstrictive activity of AVP on several vascular beds has been observed in both adult and fetal mammals (Iwamoto, Rudolph, Keil & Heymann, 1979). It has also been suggested that the haemodynamic effects of AVP are of more importance at an early age than later in life (Herin, Eklof & Aperia, 1984).…”

“…It has also been suggested that the haemodynamic effects of AVP are of more importance at an early age than later in life (Herin, Eklof & Aperia, 1984).…”