Atrial extract: hemodynamics in Wistar-Kyoto and spontaneously hypertensive rats

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Abstract
Partially purified low (LMW) and high (HMW) molecular-weight atrial natriuretic extracts were administered i.v. (540 .mu.g protein/kg) to conscious Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Both LMW and HMW atrial natriuretic extracts produced an immediate decrease in mean arterial pressure that reached maximum within 5 min and returned to control levels within 30 min. In both strains, cardiac output decreased .apprx. 14% following administration of LMW. Total peripheral resistance increased only in SHR. Organ blood flow was significantly decreased to skin, brain, heart, kidneys and splanchnic organs of WKY and to skin, muscle, heart and splanchnic organs of SHR following administration of LMW. Corresponding increases in organ vascular resistance index were observed in brain, heart and splanchnic organs of WKY and in skin, heart and splanchnic organs of SHR. To some extent, the changes in organ blood flow may be a reflection of the decrease in cardiac output induced by LMW. After administration of HMW, no significant changes were observed in cardiac output or total peripheral resistance, although they tended to decrease. Organ vascular resistance was decreased to skin, muscle, brain and splanchnic organs of SHR. Little difference was observed between WKY and SHR responses to atrial natriuretic extracts. Atrial natriuretic extracts apparently have an effect on systemic and regional hemodynamics in conscious rats that differs markedly from those of vasodilators such as nitroglycerin or hydralazine.

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