Physiological Changes in Androgen Plasma Levels with Elapsing of Time from Castration in Adult Male Rats

Abstract

In the present study we investigated in adult male rats the effects of castration on Dehydroepiandrosterone (DHEA), Androstenedione (Δ4), Testosterone (T) and Dihydrotestosterone (DHT) plasma levels: five days (group II), seven weeks (group III) and eleven weeks (group IV) after orchiectomy. The same hormone assays were performed in rats approximately 60 days of age which underwent a sham-operation for orchiectomy (group I). Our data show that five days following orchiectomy (group II) Δ4, T and DHT were decreased with respect to sham-operated rats. (Group I: Δ4: 83.3±14.9 (SEM) ng/dl (n=12); T: 435.32±51.45 (n=12); DHT: 51.47±6.54 (n=12); Group II: Δ4: 44.81±6.09 (n=12) P = 0.05; T: 25.54±2.88 (n=12) P < 0.01; DHT: 12.9±2.51 (n=12) P < 0.01). Seven weeks afterwards T and DHT remained significantly lower (group III: T: 54.37±12.21, n=16) (P < 0.01; DHT: 33.22±4.49 (n=16) P < 0.01) while eleven weeks after all steroids were significantly decreased with respect to the values observed in sham-operated rats. (Group IV) Δ4: 32.01±5.7 (n=10) P < 0.01; T: 27.29±7.05 (n=10) P < 0.01; DHT: 29.03±5.34 (n=10) P < 0.01). In all three groups of castrated animals the Δ4/T ratio appeared significantly augmented (group I: 0.24±0.007 (n=12); group II: 2.27±1.7 (n=12) P < 0.01; group III: 2.07±0.7 (n=11) P < 0.001; group IV: 1.47±0.85 (n=10) P < 0.01) while the T/DHT ratio was significantly lower with respect to the sham-operated rats (group I: 9.36±0.93 (n=12); group II: 2.57±0.32 (n=12) P < 0.01; group III: 2.12±0.48 (n=16) P < 0.01; group IV: 1.02±0.15 (n=10). This suggests that DHT in orchiectomized rats could be derived from other precursors than T. Five days after castration (group II) DHEA was positively related to Δ4 (r=0.74 (n=12) 0.02 > P > 0.01) and both steroids were negatively related to T (DHEA: r=-0.79 (n=12) P<0.01; Δ4: r=-0.80 (n=12) P < 0.01) while in group IV an inverse correlation appeared between the DHEA/Δ4 ratio and T circulating levels (r=-0.648 (n=10) P=0.05). This emphasizes the role of DHEA and Δ4 in maintaining testosterone circulating levels. Finally in the same two groups the negative correlation observed between the Δ4/T and T/DHT ratios (group III: r=-0.68 (n=11) P < 0.05; group IV: r=-0.63 (n=10) P = 0.05) indicates an important contributory role of Δ4 in affecting circulating levels of DHT in adult orchiectomized rats with the elapsing of time after castration.