CHANGES IN THE MESSENGER-RIBONUCLEIC-ACID FOR INSULIN-LIKE GROWTH-FACTOR-I AND -II IN THE PORCINE TESTIS DURING AND BETWEEN 2 WAVES OF TESTICULAR DEVELOPMENT

The boar testis was used as a model for examining the possible role of production of the insulin-like growth factors (IGF) in steroidogenesi s and/or testicular growth as testicular development occurs in waves. Blood and testes were sampled from boars at different ages (100-102 da ys of gestation; 7, 19, and 30 days; and 10 and 25 wk), selected to oc cur during and between the last two waves of testicular development. S erum was analyzed for testosterone and RNA was extracted from the test es for Northern and dot-blot analysis of IGF mRNA. Testosterone concen trations declined (P = 0.01) from 7 days to 10 wk of age and rebounded at 25 wk, indicating completion of the second and third waves of test icular development. The quantity of testicular mRNA for IGF-I increase d gradually with age, and that for IGF-II decreased. We therefore conc lude that regulation of the expression of the mRNAs for IGF-I and -II in the pig testis is not a function of either the waves of testicular development or the level of steroidogenesis.