Vascular alpha1-adrenoceptors in isolated perfused rat kidney: influence of ageing.

1. The present study identifies alpha1-adrenoceptor subtype(s) involved in constrictor responses of the kidney and how ageing influences it. 2. The study was conducted on kidneys from F344BNF1 rats, which unlike F344 or Wistar rats used by many previous investigators do not exhibit glomerulonephritis at advanced age. 3. Noradrenaline (NA) and phenylephrine (PHE) (non-selective alpha1) and A61063 (selective alpha(1A)) adrenoceptor agonists elicited constriction of perfused kidneys of young and old rats. The pD2 values (index of renovascular reactivity) were significantly higher for A61603 than for either PHE or NA, and significantly decrease across age groups. 4. BMY 7378 or RS 100329, alpha(1D)- or alpha(1A)-adrenoceptor antagonists, respectively antagonized the constrictor responses and suppressed the maximal responses to all agonists in young adult rat kidneys. However, antagonism of PHE or A61063 by BMY 7378 in old rat kidneys was surmountable. 5. This study suggests that: (i) alpha(1A) and alpha(1D)-adrenoceptor subtypes mediate vasoconstriction of perfused rat kidney; (ii) alpha(1A)-adrenoceptor subtype appears to predominate in renal vasculature based on agonist relative potencies. (iii) Ageing significantly decreases alpha1-adrenoceptor-mediated vasoconstriction of rat kidney.