Published: 22 August, 2018 | Volume 2 - Issue 1 | Pages: 014-025
Background: C-type natriuretic peptide (CNP) was isolated from porcine brain and is a 22-amino acid peptide which belongs to the natriuretic peptide (NP) family. Even though this peptide shares structural similarity to other endogenous NPs including atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) its receptor selectivity is different from other NPs. The present study was undertaken to investigate the expression of C-type natriuretic peptide (CNP) and its specific guanylyl cyclase (GC)-coupled receptor in the granulosa cells of the pig ovarian follicle.
Results: Specific 125I-[Tyr0]-CNP(1-22) binding sites were localized in the granulosa cell layer of the ovarian follicle with an apparent dissociation constant (Kd>) and a maximal binding capacity (Bmax) of 1.41±0.39 nM and 2.75±0.65 fmol/mm2 respectively. Binding of 125I-[Tyr0]-CNP(1-22) to these sites was also prevented by atrial natriuretic peptide (ANP(1-28)), brain natriuretic peptide (BNP(1-26)) and des[Gln18,Ser19,Gly20, Leu21,Gly22] ANP(4-23) (C-ANP). Production of 3’,5’-cyclic guanosine monophosphate (cGMP) by particulate GC in the granulosa cell membranes was stimulated by natriuretic peptides (NPs) with a rank order of potency of CNP(1-22)>>BNP(1-26)>ANP(1-28). HS-142-1, a selective antagonist of the two recognized GC-coupled NPRs, inhibited CNP(1-22)-stimulated cGMP production in granulosa cell membranes in a dose-dependent manner. Also mRNAs for all three recognized NPRs were detected in granulosa cells using reverse transcriptase-polymerase chain reaction (RT-PCR). Serial dilution curves of granulosa cell extracts were parallel to the standard curve of synthetic CNP.
Conclusion: These results indicate that CNP and its specific receptor are expressed in the granulosa cells of the pig ovary, and suggest that CNP may be a local autocrine and/or paracrine regulator via activation of its specific GC-coupled receptor, NPR-B.
Natriuretic peptide receptor; Autoradiography; RT-PCR; Granulosa layer; Pig ovary; C-Type natriuretic peptide; Particulate guanylyl cyclase; Cgmp