The calcium entry blocker verapamil increases red cell flux in the vasa recta of the exposed renal papilla.
To investigate the vasoreactivity of the vessels of the juxtamedullary vasculature, measurements were made of the red blood cell flux (Qrbc) in the vasa recta of the exposed renal papilla of anaesthetized rats by means of fluorescently labelled erythrocytes. The flux was measured before and after intravenous administration of the calcium entry blocker verapamil, which was infused in two different doses. A control group receiving vehicle was studied in parallel. The lower dose of verapamil (0.6 mg h-1 kg-1 body wt) increased Qrbc by 30 +/- 6% (n = 9, P less than 0.05, mean +/- 1 SEM) and reduced the systemic blood pressure by 6% (P less than 0.05). The osmolality of urine samples from the papillary tip remained statistically unchanged (1199 +/- 60 vs. 1186 +/- 102 mosM kg-1 H2O). In the animals receiving the higher dose of verapamil (2.4 mg h-1 kg-1 body wt), Qrbc increased by 39 +/- 7% (n = 10, P less than 0.05) and the blood pressure was reduced by 9% (P less than 0.05), while urine osmolality was unchanged (1104 +/- 110 vs. 1264 +/- 123 mosM kg-1 H2O). In the time control group there was no statistically significant change in Qrbc (+6 +/- 8%, n = 10), blood pressure or urine osmolality (1006 +/- 61 vs. 1091 +/- 70 mosM kg-1 H2O). The verapamil-induced increase in Qrbc is probably mainly mediated by a relaxation of the afferent arteriole of the juxtamedullary nephrons. The results confirm our previous indication of a high vasoreactivity in the vessels of the juxtamedullary vasculature.(ABSTRACT TRUNCATED AT 250 WORDS)
Hansell
P
P
Department of Physiology and Medical Biophysics, University of Uppsala, Sweden.
Sjöquist
M
M
Ulfendahl
H R
HR
D000818:Animals; D002121:Calcium Channel Blockers / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004906:Erythrocyte Count; D004911:Erythrocyte Volume; D004912:Erythrocytes / Q000187:drug effects*; D005260:Female; D007606:Juxtaglomerular Apparatus / Q000098:blood supply*; D007668:Kidney / Q000187:drug effects*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014655:Vascular Resistance / Q000187:drug effects*; D014700:Verapamil / Q000008:administration & dosage*
D002121:Calcium Channel Blockers; D014700:Verapamil