Differential regulation of mesenteric and femoral blood flow in the rat as revealed by computerized data acquisition and evaluation

• 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 ultrasonic transit time shift technique. The signals for arteial blood pressure and BF were fed into a personal computer via an analogue-digital converter. Mean arterial blood pressure, heart rate and vascular conductance (CV) were calculated on-line. For subsequent analysis of the data, algorithms were programmed to filter the data, and to determine average and peak values for each parameter.

• 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 accompanied by constriction of the mesenteric artery. In contrast, the femoral artery responded to phenylephrine with constriction, to angiotensin II with dilatation and to arginine vasopressin with dilation followed by constriction. The haemodynamic effects of endothelin-1 (0.03–3.0 nmol kg⁻¹) were generally biphasic, the initial hypotension being associated with dilatation, and the delayed hypertension being accompanied by constriction of both the mesenteric and femoral arterial bed.

• Terbutaline (3–1.0 nmol kg⁻¹) and calcitonin gene-related peptide (0.03–1 nmol kg⁻¹) caused systemic hypotension along with mesenteric and femoral vasodilatation.

• Telmisartan (1 mg kg⁻¹), an angiotensin AT₁ receptor antagonist, dilated the mesenteric artery, but had no effect on femoral VC. In contrast, the α₁-adrenoceptor antagonist prazosin (0.1 mg kg⁻¹), dilated the femoral artery without altering mesenteric VC. Similarly, the β-adrenoceptor antagonist propranolol (1 mg kg⁻¹) had no effect on mesenteric VC, but constricted the femoral arterial bed.

• These data demonstrate that the haemodynamic effects of exogenously administered drugs can widely differ between the mesenteric and femoral arterial beds of urethane-anaesthetized rats. Furthermore, 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 demonstrates 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 study.