Endothelins (ET) are potent vasoconstrictive peptides originally isolated from vascular endothelial cells. Their biological effects are mediated through two different receptors, the endothelin-1 (ET-1)-selective endothelin receptor subtype ETA and the non-selective receptor subtype ETB. ET-1 protein has been found in human ovarian follicular fluid and ET-1 mRNA expression has been demonstrated in ovarian tissue. These findings indicate that the endothelin-system participates in the modulation of ovarian function, probably acting in an autocrine/paracrine manner. In the current study we used freshly aspirated, luteinized human granulosa cells (hGC) representing an in vitro model of the early corpus luteum. By means of RT-PCR and immunocytochemistry we investigated whether luteinized human granulosa cells express ETA and ETB receptors. Specific amplification products of ETA transcripts were detected in all samples investigated. In contrast, only after using a three-fold amount of ETB reverse transcripts we were able to demonstrate specific, but weak amplification products. In addition, immunocytochemical staining for ETA but not for ETB was found in granulosa cell preparations. The present study provides clear evidence that human granulosa cells predominantly express ETA receptor subtype mRNA and protein hinting to its possible role in follicle maturation and corpus luteum formation.

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The levels of total human serum RNAase activity (HSRA) from 24 patients with ovarian cancer have been followed up for a period of over 5 months. The determinations of HSRA were carried out according to our assay system described earlier. Two representative patterns of the HSRA are presented, one from a patient with an ascertained remission of an ovarian carcinoma. Increasing HSRA values are concomitant with tumor progression while in remission the HSRA remains at normal rates. We have reported earlier that optimum HSRA depends on physiological concentrations of NaCl in the reaction mixture. However, NaCl can be replaced by KCl without a loss of activity. No correlation was detectable between increased HSRA and an excessive electrolyte content in serum. The mixtures of sera with various RNAase activities showed linear additivity. These findings suggest that an increased concentration of the RNAases normally present in human serum and/or additional RNAases are responsible for the increase of the HSRA.