AGE-RELATED-CHANGES IN ALPHA(1)-ADRENOCEPTORS IN RAT PROSTATE

The age-related changes in the density of alpha(1)-adrenoceptors in th e dorsolateral lobe of the rat pros tate were evaluated in Wistar rats at 8, 52, and 104 weeks of age. [H-3]YM617, a newly synthesized alpha (1)-adrenergic blocker, was used as the ligand. The mean maximum numbe r of binding sites, or alpha(1)-adrenoceptor density (B-max) +/-SE of 104-week-old rats (11.0+/-1.2 fmol/mg protein) was significantly lower than that in the 8-week-old rats (37.0+/-4.3 fmol/mg protein) and 52- week-old rats (37.2+/-3.4 fmol/mg protein) (respectively, P < 0.01). I n contrast, mean affinity (K-d) values +/-SE of these groups showed no significant differences (8-week-old rats, 115.8+/-9.1; 52-week-old ra ts, 100.5+/-5.8; and 104-week-old rats, 116.4+/-9.8 pM). Mean volumes +/-SE of muscle cells oi the prostate were 3.7+/-1.1x10(3) mu m(3) at 8 weeks, 30.0+/-6.2x10(3) mu m(3) at 52 weeks, and 18.6+/-8.2x10(3) mu m(3) at 104 weeks. Volumes for 8-week-old rats were significantly sma ller than those for 52-week-old (P < 0.01) and 104-week-old rats (P < 0.05). However, the mean area density of the muscle cells showed no di fference among the three groups: 20.1+/-2.2% at 8 weeks, 27.3+/-2.9% a t 52 weeks and 20.3+/-3.4% at 104 weeks. In conclusion, the density of YM617-binding sites (alpha(1)-adrenoceptors) in 104-week-old rats was lower than in 8- and 52-week-old rats. Muscle volume in the rat prost ate was larger in rats aged 52 and 104 weeks than in 8-week-old rats, but no correlation was found between alpha(1)-adrenoceptor density and the muscle volume or muscle density in aging.