1. The possible contribution of changes in cardiac β-adrenoceptors to alterations in cardiac responses to isoprenaline were investigated in hearts isolated from rats with renovascular hypertension (two-kidney, one-clip Goldblatt), 6, 12 and 18 weeks after renal artery clipping. Cardiac responses were determined in vitro (Langendorff preparation), and ventricular β-adrenoceptors ([ 3 H)dihydroalprenolol, [ 3 H]DHA) were then assayed in the same 44 hearts. 2. There was no difference between renovascular hypertensive rats (RHR) and matched normotensive controls as regards chronotropic responses to isoprenaline or in atrial β-adrenoceptor numbers or apparent affinity. 3. Inotropic responses were significantly lower in all stages of RHR than in matched normotensive controls. 4. There was also a significant ( P < 0.001) decrease in ventricular β-adrenoceptor density with no significant change in apparent affinity ( K d ). Inotropic responsiveness to isoprenaline (max. increment in peak d P /d t ) was significantly correlated with ventricular β-adrenoceptor density ( r = 0.54, P = 0.0005). 5. These results suggest that the reduction of ventricular β-adrenoceptor density in that model of hypertension was responsible, at least partially, for the lowered inotropic responsiveness of the same hearts to isoprenaline.
1. A general method for the development of a blood volume index was devised to allow inter-individual comparisons. 2. An accurate and acceptable blood volume index had to fulfil certain criteria; it had to be (1) not correlated with body size, (2) highly correlated with blood volume, (3) either dimension-less or expressible in units of length or of surface area and (4) simple to calculate. 3. Available data, from the Broussais Hospital, Paris, the Zuiderziekenhuis, Rotterdam and the Cleveland Clinic, Cleveland, Ohio, included six groups of normal subjects, male essential hypertensive patients and female essential hypertensive patients. 4. Extensive calculations, based on the available data, indicated that the equation BVI = BV/( a√H.W ) (BVI = blood volume index, BV = blood volume, H = body height, W = body weight and a = a constant depending on the chosen units) was the simplest index which satisfied the above requirements. 5. As the equation SA = 0.165 √( H.W ) (SA = body surface area, in m 2 , H in m and W in kg) is almost identical with the Dubois & Dubois formula predicting body surface area from height and weight, one may choose a = 0165 and the index BVI = BV/[0.165 √( H.W )] (/ H in m, W in kg, BV in ml and BVI in ml/m 2 ). Thus blood volume is referred to body surface area. 6. Blood volume referred to unit body surface area appears, at the present, to be the most appropriate ‘blood volume index’. However, studies of data from larger groups and from more centres are needed to confirm this conclusion.