DIFFERENTIAL REGULATION OF MESENTERIC AND FEMORAL BLOOD-FLOW IN THE RAT AS REVEALED BY COMPUTERIZED DATA-ACQUISITION AND EVALUATION

1 A set-up for computerized acquisition and evaluation of haemodynamic data was constructed. Blood flow (BF) in the superior mesenteric and femoral artery of urethane-anaesthetized rats was measured with the ul trasonic transit time shift technique. The signals for arterial blood pressure and BF were fed into a personal computer via an analogue-digi tal converter. Mean arterial blood pressure, heart rate and vascular c onductance (CV) were calculated on-line. For subsequent analysis of th e data, algorithms were programmed to filter the data, and to determin e average and peak values for each parameter. 2 Systemic hypertension induced by phenylephrine (3-300 nmol kg(-1)), angiotensin II (0.1-3.0 nmol kg(-1)) and arginine vasopressin (0.03-1.0 nmol kg(-1)) was accom panied by constriction of the mesenteric artery. In contrast, the femo ral artery responded to phenylephrine with constriction, to angiotensi n II with dilatation and to arginine vasopressin with dilation followe d by constriction. The haemodynamic effects of endothelin-1 (0.03-3.0 nmol kg(-1)) were generally biphasic, the initial hypotension being as sociated with dilatation, and the delayed hypertension being accompani ed by constriction of both the mesenteric and femoral arterial bed. 3 Terbutaline (3-1.0 nmol kg(-1)) and calcitonin gene-related peptide (0 .03-1 nmol kg(-1)) caused systemic hypotension along with mesenteric a nd femoral vasodilatation. 4 Telmisartan (1 mg kg(-1)), an angiotensin AT(1) receptor antagonist, dilated the mesenteric artery, but had no effect on femoral VC. In contrast, the alpha(1)-adrenoceptor antagonis t prazosin (0.1 mg kg(-1)), dilated the femoral artery without alterin g mesenteric VC. Similarly, the beta-adrenoceptor antagonist propranol ol (1 mg kg(-1)) had no effect on mesenteric VC, but constricted the f emoral arterial bed. 5 These data demonstrate that the haemodynamic ef fects of exogenously administered drugs can widely differ between the mesenteric and femoral arterial beds of urethane-anaesthetized rats. F urthermore, vascular tone of these two arterial beds in maintained by different vasoconstrictor systems. While the femoral artery is mainly under adrenergic control, the renin-angiotensin axis is predominant in the mesenteric arterial bed. In addition, this study also demonstrate s that computerized analysis enables quick and accurate estimation of haemodynamic drug effects, and is superior to 'by hand' evaluation of peak changes in the functional diameter of the vascular bed under stud y.