Objective: The prepro-adrenomedullin gene encodes the biologically active peptide adrenomedullin, which acts as a potent vasodilator as well as a modulator of vascular smooth muscle cell growth. We investigated the question of whether adrenomedullin is regulated in response to metabolic perturbations in vascular smooth muscle.
Materials and methods: Acute inhibition of glycolysis, leading to partial depletion of cellular ATP, was produced in cultured rat aortic vascular smooth muscle cells by replacing glucose with 2-deoxyglucose. Solution hybridization/RNase protection analysis was used to quantitate changes in expression of the prepro-adreno-medullin messenger RNA and a specific radioimmunoassay was used to assess levels of secreted adrenomedullin.
Results: Acute incubation of rat aortic vascular smooth muscle cells with 2-deoxyglucose caused a rapid and sustained induction of low basal levels of adrenomedullin messenger RNA, which reached twice the control levels by 1 h and four times control levels by 6 h. The induction of adrenomedullin messenger RNA expression was dependent upon de-novo gene transcription and was reversed by the re-introduction of glucose. Despite the sustained increase in adrenomedullin messenger RNA, secretion of immunoreactive-adrenomedullin from vascular smooth muscle cells was reduced by as much as 75% and paralleled the inhibition of radiolabeled amino acid incorporation into protein during glycolytic inhibition; both parameters recovered towards control levels following re-introduction of glucose.
Conclusions: The rapid and reversible activation of the adrenomedullin gene and inhibition of adrenomedullin peptide release in response to metabolic inhibition suggest that adrenomedullin represents a novel localized mechanism that may modulate regional blood flow and vascular smooth muscle cell proliferation in response to perturbations of normal metabolism.