Age-related changes in alpha 1-adrenoceptors in rat prostate.

The age-related changes in the density of alpha 1-adrenoceptors in the dorsolateral lobe of the rat prostate were evaluated in Wistar rats at 8, 52, and 104 weeks of age. [3H]YM617, a newly synthesized alpha 1-adrenergic blocker, was used as the ligand. The mean maximum number of binding sites, or alpha 1-adrenoceptor density (Bmax) +/- 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). In contrast, mean affinity (Kd) values +/- SE of these groups showed no significant differences (8-week-old rats, 115.8 +/- 9.1; 52-week-old rats, 100.5 +/- 5.8; and 104-week-old rats, 116.4 +/- 9.8 pM). Mean volumes +/- SE of muscle cells of the prostate were 3.7 +/- 1.1 x 10(3) microns3 at 8 weeks, 30.0 +/- 6.2 x 10(3) microns3 at 52 weeks, and 18.6 +/- 8.2 x 10(3) microns3 at 104 weeks. Volumes for 8-week-old rats were significantly smaller 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 difference among the three groups: 20.1 +/- 2.2% at 8 weeks, 27.3 +/- 2.9% at 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.(ABSTRACT TRUNCATED AT 250 WORDS)