The collagen content of the gubernaculum during testicular descent in the pig fetus.

Contracture of collagen fibres in the gubernaculum has been suggested as a mechanism responsible for fetal descent of the testis. We measured the collagen content of the gubernaculum, fetal thigh muscle and umbilical cord tissue by assaying its hydroxyproline and protein content in 194 male pig fetuses between 60 and 109 days of gestation. During the period of testicular descent (80-90 days of gestation), a decrease occurred in the hydroxyproline/wet mass and protein/wet mass of the gubernaculum, but not of fetal striated muscle or umbilical cord tissue, reflecting an increase in the water content of the gubernaculum during this period. An increase occurred in the hydroxyproline/protein concentration of the gubernaculum and fetal striated muscle, but not of umbilical cord tissue, denoting an accumulation of collagen in the gubernaculum after descent of the testis. In view of the absence of a firm distal attachment of the gubernaculum in the pig fetus, the increase in its collagen content is probably not a cause of descent by exerting traction on the testis, but merely reflects the involution of the gubernaculum noted after descent.