Masayasu Iwabuchi

Distribution and concentration of urocortin, and effect of adrenalectomy on its content in rat hypothalamus

We developed a specific and sensitive radioimmunoassay (RIA) for rat urocortin (rUcn) and investigated the tissue distribution and concentration of immunoreactive (IR-)Ucn in rats. Antiserum was obtained by immunizing rabbits with synthetic rUcn21-35 coupled with bovine thyroglobulin. 125I-[Tyr]18-rUcn19-37 was used as the tracer. The RIA detected synthetic rUcn1-40 as low as 0.4 fmol/tube, and did not cross-react with other corticotropin-releasing factor-related peptides. IR-Ucn was widely distributed in central nervous system, endocrine organs, and digestive system. Its concentration was highest in pituitary (11.0 +/- 1.36 pmol/g.w.w., mean +/- SEM, n=4). Reverse-phase HPLC revealed that hypothalamic IR-Ucn had similar chromatographic mobility to synthetic rUcn1-40. However, bilateral adrenalectomy did not influence the hypothalamic IR-Ucn content. Our results suggest that Ucn may play important roles in various tissues in normal rats, but not behave as a hypothalamic hypophysiotropic factor in mediating adrenocorticotropin secretion in adrenalectomized rats.

Urocortin in human placenta and maternal plasma

Plasma immunoreactive (IR-) urocortin (Ucn) and corticotropin-releasing factor (CRF) levels in pregnant women were measured by their specific radioimmunoassays after extraction. Although plasma IR-CRF levels were increased in pregnant women as compared to men and non-pregnant women, there was no difference of plasma IR-Ucn levels among groups. Ucn mRNA was detected in cytotrophoblasts and syncytiotrophoblasts by in situ hybridization. A reverse-phase high-performance liquid chromatography (HPLC) showed the major peak of IR-Ucn in placenta and plasma that had similar chromatographic mobility to synthetic Ucn1-40. These data suggest that Ucn is produced and processed into the same form of synthetic Ucn in placenta, but not secreted into maternal blood.

Effect of Urocortin and Its Interaction with Adrenocorticotropin (ACTH) Secretagogues on ACTH Release

We examined the effect of urocortin (Ucn) on the adrenocorticotropin (ACTH) release from cultured rat anterior pituitary cells and AtT 20 cells. Synthetic rat (r)Ucn was not soluble in 0.1 N HCl but soluble in alkaline solvents with diminished corticotropin-releasing activity. rUcn dissolved in 0.1 M sodium phosphate buffer as a stock solution maintained its bioactivity and had the equal corticotropin-releasing activity with rat/human corticotropin-releasing factor (r/hCRF). rUcn stimulated the adrenocorticotropin release via CRF-receptors accompanied by the additive effect with r/hCRF, the synergistic effect with arginine vasopressin and the dose-dependent inhibition of a potent CRF-receptor antagonist.

Stimulatory Effect of Calcitonin Gene-Related Peptide on Adrenocorticotropin Release from Rat Anterior Pituitary Cells

In the present study, we examined the direct regulatory effect of rat calcitonin gene‐related peptide (CGRP) on adrenocorticotropin (ACTH) release from rat cultured anterior pituitary cells. CGRP significantly increased ACTH release at concentrations of 10−8–10−11 M. The ACTH release was gradually increased by CGRP concentrations lower than 10−10 M, and was decreased at concentrations higher than 10−9 M, presenting a bell‐shaped dose‐response curve. As well as having an additive effect on corticotropin‐releasing factor‐induced ACTH release, CGRP stimulated the accumulation of intracellular cAMP. The CGRP‐induced ACTH release was inhibited by a protein kinase A inhibitor, suggesting that its stimulatory effect on the ACTH release was mediated via an adenylate–cyclase–protein kinase system. CGRP‐like immunoreactive nerve fibers have been reported to innervate the anterior pituitary, so that the stimulatory effect of CGRP on the ACTH release suggests that this peptide may be involved in neural regulation of hormone secretion in the anterior pituitary.

Adrenal adenoma with bilateral adrenocortical nodular change in a patient with Cushing's syndrome.

We report a 57‐year‐old male patient with adrenocorticotrophin (ACTH)‐independent Cushings syndrome and long‐standing hypertension. Both abdominal computed tomographic scan and magnetic resonance imaging revealed bilateral adrenal enlargement with the presence of a tumour in the left adrenal. Marked uptake of 131I‐6β‐iodomethyl‐19‐norcholesterol was observed only in the left adrenal gland. Left adrenalectomy and biopsy of the right adrenal gland were subsequently performed. Histological examination revealed the presence of an adrenocortical adenoma in the left adrenal with multiple adrenocortical nodules in both left and right non‐neoplastic adrenals. Peri‐ and intraadrenal arteries and arterioles demonstrated marked arteriosclerotic vascular changes. Immunoreactivity for several steroidogenic enzymes was present in the tumour and markedly diminished in the non‐neoplastic adrenals. This patient with Cushings adenoma is considered to have developed adrenocortical nodules in the non‐neoplastic adrenal possibly as a result of localized compensatory overgrowth of adrenocortical cells in response to ischaemic changes due to arteriopathy. When examining patients with Cushings syndrome and bilateral adrenal enlargement, the possibility of concomitant adenoma and adrenocortical nodule formation should also be considered in the differential diagnosis.