Retrograde transfer of 125I-radiolabelled activin and inhibin in the periovarian vascular complex in the sow.

This study investigated whether activin A and an inhibin-alpha subunit fragment (INHalpha) could permeate in a periovarian vascular complex from ovarian effluent into the ovarian artery and be retrograde transferred into the ovary. Radiolabelled activin A (125I-activin A) and INHalpha (125I-INHalpha) were injected (2.7 x 10(7) dpm) into follicles or corpora lutea (CL). It was demonstrated that 125I-activin A and 125I-INHalpha were released into the ovarian effluent and permeated into the arterial blood supplying the ovary in both phases of the cycle. The concentration of 125I-activin A in ovarian arterial blood was higher in the luteal phase (LP) than in the follicular phase (FP) (P<0.0001) in contrast to 125I-INHalpha which was higher in the FP (P<0.0001). The concentration of 125I-activin A in uterine tissues generally did not differ between the phases of the estrous cycle, but the concentration of 125I-INHalpha was higher (P<0.05) in the FP than in the LP. The concentration of 125I-activin A was higher in the LP in samples of endometrium and myometrium (P<0.05), as well as mesometrium (P<0.01), and higher in the FP in samples of mesometrium (P<0.05) close to the ovary than in the samples adjoining the uterine body. In the FP, the concentration of 125I-INHalpha was higher in endometrium and mesometrium close to the ovary than in samples adjoining the uterine body (P<0.05). In conclusion, the study demonstrated that it was possible for INHalpha and activin A to be retrograde transferred to the ovary. Thus this transfer could elevate their concentration in arterial blood supplied to the ovarian follicles or CL and may influence production of these peptides in the ovary, modulating ovarian function.