| Developmental changes of serum and testicular tissue concentrations of testosterone in Erhualian and Large White boarsSerum and testicular tissue were sampled from male Erhualian and Large White boars at 3, 20, 30, 90, 120 and 180 days of age, respectively. Testosterone concentrations in serum and testicular tissue were analyzed by RIA. The results indicated that serum testosterone concentrations in both breeds presented a low level before 90 days of age. They increased significantly(p﹤0.05) at 90 and 120 days of age, respectively. However, the increase speed and extent of serum testosterone concentrations were lower in Large White boars than in Erhualian boars .In general, serum testosterone concentrations in Erhualian boars were higher(p﹤0.05)than in Large White boars. The patterns of testicular testosterone content turned out to be contrary to those of serum testosterone concentrations in both breeds. The levels were highest at 3 days of age and declined with the increase of age. They declined sharply (p﹤0.01)in Erhualian boars at 30 and 90 days of age, while declined gradually(p﹤0.05)in Large White boars from 3 to 90 days of age and varied little from 90 days of age onwards. In general, testicular testosterone content were higher(p﹤0.01) in Large White boars than in Erhualian boars.Developmental changes of GHR, IGF-I and IGF-IR mRNA level in the testis of Erhualian and Large White boarsTesticular tissue samples were collected from male Erhualian and Large White boars at 3, 20, 30, 45,90, 120 and 180 days of age, respectively. GHR, IGF-I and IGF-IR mRNA level were determined by relative quantitative RT-PCR with 18S rRNA as internal standard. The results showed that the patterns of testicular GHR mRNA level in Erhualian and Large White boars were different. GHR mRNA level in Erhualian boars increased from day 0 to 30, with two peak values appeared on day 30 and 180, and a declined value from day 45 to 120. GHR mRNA level in Large White boars was high at day 0 and declined sharply(p﹤0.05)at day 3 , which had no significant changes thereafter. As a whole, GHR mRNA level in Erhualian boars was higher than that in Large White boars (p﹤0.05 ). The patterns of testicular IGF-I mRNA level in Erhualian boars were similar with those in Large White boars from day 0 to 30, which increased with the age of boars. The levels of IGF-I mRNA in Erhualian boars had no significant changes from day 30 to 180, while those in White boars lowed at day 90 and increased thereafter (p﹤0.05 ). As a whole, IGF-I mRNA levels in Erhualian boars were higher than those in Large White boars (p﹤0.05 ). The patterns of testicular IGF-IR mRNA level in Erhualian and Large White boars were different. The levels of IGF-IR mRNA in Erhualian boars lowed from day 90 to 120(p﹤0.05 ), while maintained consistent from day 0 to 45 and day 120 to 180. IGF-IR mRNA level in Large White boars was high at day 0 and declined at day 3(p﹤0.05 ) , and maintained invariable thereafter. As a whole, the levels of IGF-IR mRNA in Erhualian boars were higher than those in Large White boars (p﹤0.05 ). GHR mRNA level correlated positively with and IGF-I mRNA level and IGF-IR mRNA level (p﹤0.05 ). The results mentioned above suggest that GHR, IGF-I and IGF-IR mRNA in porcine testis were expressed according breed specific developmental patterns, GH acted directly at the testicular tissue and regulated it's growth and function, and GH contributed to the expression of testicular IGF-I and IGF-IR mRNA.Effect of GH on testosterone secretion by porcine Leydig cells in vitroLeydig cells from 18 days old boars were incubated with or without rpGH in the presence or absence of hCG, and testosterone levels in the medium were measured by RIA. The results showed that hCG increased testosterone production in a dose- and time-dependent manner. The sensitivity declined following the repeated hCG stimulate. Steroidogenesis was inhibited by rpGH in a dose-dependent manner in the absence of hCG, and the sensitivity changed with time. However, rpGH increased hCG-induced testosterone production in a dose- and time-dependent manner and the sensitivity changed with the concentrations of hCG. In the presence of hCG at a high dose (20IU/ml), the sensitivity was higher and Leydig cell responsiveness maintained shorter. In the presence of hCG at a low dose (10IU/ml), the sensitivity was lower and Leydig cell responsiveness maintained longer. These results demonstrated that GH worked in partnership with LH/hCG and it's effect on testosterone secretion was LH/hCG-dependent. |
PDF Full Text Request