Adrenomedullin Enhances Cell Proliferation and Deoxyribonucleic Acid Synthesis in Rat Adrenal Zona Glomerulosa: Receptor Subtype Involved and Signaling Mechanism

Abstract

The effect of adrenomedullin (ADM) on the proliferative activity of the rat adrenal cortex has been investigated in vivo, using an in situ perfusion technique of the intact left gland. ADM and other chemicals were dissolved in the perfusion medium, and the perfusion was continued for 180 min. ADM infusion concentration dependently increased the mitotic index and [3H]thymidine incorporation into DNA in the zona glomerulosa (ZG; the maximal effective concentration was 10(-8) M), but not in inner adrenocortical layers, where basal proliferative activity was negligible. The effect of 10(-8) M ADM was equipotently counteracted by both the calcitonin gene-related peptide (CGRP) type 1 receptor antagonist CGRP-(8-37) and ADM-(22-52). The adenylate cyclase inhibitor SQ-22536 (10(-4) M), the cAMP blocker Rp-cAMP-S (10(-3) M), and the protein kinase A inhibitor H-89 (10(-5) M), although counteracting the ZG proliferogenic action of 10(-9) M ACTH, did not affect the 10(-8) M ADM-elicited increase in ZG DNA synthesis. Similar results were obtained using the phospholipase C inhibitor U-73122 (10(-5) M), the inositol-1,4,5-trisphosphate antagonist D,L-myo-inositol-1,4,5-trisphosphothiate (10(-4) M), and the protein kinase C inhibitor calphostin C (10(-5) M), which, however, significantly inhibited the ZG proliferogenic effect of 10(-9) M angiotensin II. The growth-promoting action of 10(-8) M ADM was not affected by the phospholipase A2 inhibitor AACOCF3 (10(-5) M), the cyclooxygenase (COX) inhibitor indomethacin (10(-5) M), or the mixed COX/lipoxygenase inhibitor phenidone (10(-5) M). In contrast, the ZG proliferogenic effect of 10(-8) M ADM was abolished by either the tyrosine kinase (TK) inhibitor tyrphostin-23 (10(-5) M) or the mitogen-activated protein kinase (MAPK) antagonists PD-98059 and U0216 (10(-4) M). ADM (10(-8) M) stimulated TK and p42/p44 MAPK activity in dispersed ZG, but not ZF, cells, and the effect was reversed by either 10(-6) M CGRP-(8-37) and ADM-(22-52) or preincubation with 10(-5) M tyrphostin-23. Collectively, our findings indicate that 1) ADM stimulates cell proliferation in the rat ZG, through CGRP-(8-37)- and ADM-(22-52)-sensitive receptors, probably of the CGRP1 subtype; and 2) the mitogenic effect of ADM is mediated by activation of the TK-MAPK cascade, without any involvement of the adenylate cyclase/protein kinase A-, phospholipase C/protein kinase C-, and COX- or lipoxygenase-dependent signaling pathways.

Endothelin‐1[1–31], acting as an ETA‐receptor selective agonist, stimulates proliferation of cultured rat zona glomerulosa cells

“…Dispersed cells were lysed as previously described [12], and then were Dounce homogenized (20 strokes; Kontes, Vineland, NJ, USA) on ice for 1 min. Homogenates were centrifuged at 4°C at 800× g for 10 min, and then at 12 000× g for 15 min.…”

Orexins stimulate glucocorticoid secretion from cultured rat and human adrenocortical cells, exclusively acting via the OX1 receptor

“…The adenylate cyclase inhibitor SQ-22536, the phospholipase C (PLC) inhibitor U-73122, the protein kinase (PK) A inhibitor H-89 and the PKC inhibitor calphostin-C (for references, see [22]) were obtained from BIOMOL Research Laboratories (Milan, Italy). Dulbecco's modified minimum essential medium (DMEM), fetal calf serum (FCS), and all other chemicals were provided by Sigma-Aldrich Corporation (St. Louis, MO).…”

G Protein Receptors 7 and 8 Are Expressed in Human Adrenocortical Cells, and Their Endogenous Ligands Neuropeptides B and W Enhance Cortisol Secretion by Activating Adenylate Cyclase- and Phospholipase C-Dependent Signaling Cascades

“…No amplification with water instead of RNA is shown as a negative control. Bottom, Real-time PCR of the effects of 10 Ϫ7 M NPB and NPW on StAR, CYP17, and CYP11B1 (adrenals [13][14][15][16]. Bars, Mean Ϯ SEM (n ϭ 4).…”