Evidence for Relaxin and Progesterone Synchronous Secretion on Days 13 to 17 of the Oestrous Cycle in Sows1)

Abstract

Concentrations of relaxin in both the utero-ovarian vein (UOV) and jugular vein (JV) as well as those of progesterone and prostaglandin F2 alpha in the UOV were studied on Days 13-17 of the oestrous cycle in sows. Mean relaxin plasma concentrations in the UOV and JV were correlated (r = 0.55; P less than 0.001) and were significantly higher (P less than 0.01) in the UOV (1.67 +/- 0.07 ng/ml), than in the JV (0.59 +/- 0.1 ng/ml). The great similarity between relaxin and progesterone profiles was ascertained (r = 0.57; P less than 0.001). The steep decrease of progesterone plasma concentration on the day of luteolysis was observed together with synchronous relaxin concentration decline. A significant correlation between relaxin and PGF2 alpha plasma concentration was demonstrated one day before luteolysis (r = 0.41; P less than 0.001).