Hiroo Imura

Presence of immunoreactive β-endorphin in plasma of patients with Nelson's syndrome and Addison's disease

Abstract A sensitive radioimmunoassay for β-endorphin (β-EP) has been developed with an antiserum obtained from a guinea pig immunized with β-EP which was contained in crude porcine ACTH preparations (Organon). The minimal detectable quantity of β-EP was 1 pg. This antibody has the same affinity for β-EP and β-LPH on a molar basis, but human ACTH, α-MSH, β-MSH, α-EP, γ-EP, Met 5 -Enkephalin and Leu 5 -Enkephalin failed to displace 125 I-β-EP from its antibody. Utilizing this radioimmunoassay we have demonstrated the existence of β-EP in plasma from patients with Nelsons syndrome and Addisons disease.

Endothelin in Human Disease. I: Essential Hypertension, Vasospastic Angina, Acute Myocardial Infarction, and Chronic Renal Failure

Following the discovery of endothelin-1 in culture medium of porcine aortic endothelial cells,’ several hundred papers have been published concerning the biological properties of endothelin-1. Studies were performed in experimental animals and isolated vessels and show that endothelin-1 has both vasoconstricting and vasodilating activities.1–5 Vasoconstricting activity results from the increase in the intracellular calcium concentration in vascular smooth muscle cells,1–4 and vasodilation is related to the production of endothelium-derived relaxing factor and prostanoids by endothelin-1.3’5 It was also reported that endothelin-1 causes proliferation of vascular smooth muscle cells6 and mediates the release of hormones involved in the control of water, electrolytes, and blood pressure, such as atrial natriuretic peptide,7,8 aldosterone,9 and renin.10 Experimental results indicate that endothelin-1 is involved in the control of cardiovascular homeostasis and in the pathophysiology of cardiovascular disorders (see Chapter 16).

The antigenic use of periodate-treated adrenocorticotropic hormone (ACTH)☆

Abstract Periodate-treated porcine ACTH, which is biologically inactive but retains its immunologic activity, was used to induce antibodies in rabbits. One such antiserum obtained after 10 months of immunization has been characterized. It differs from antisera to unmodified ACTH in several important ways: it is of higher titer than obtained previously by the use of unmodified ACTH, shows species specificity, reacts well with biologically active short-chain ACTH peptides, and neutralizes the steroidogenic effect of natural ACTH. As little as 0.2 μg of human ACTH can be detected with a radioimmunoassay using this antiserum. Periodate treatment of ACTH appears to be a promising method for producing ACTH antisera for immunoassay.

Natriuretic Peptide System in the Brain and Its Implication in Central Cardiovascular Regulation

Atrial natriuretic peptide (ANP) is a peptide hormone first isolated from the cardiac atrium and it possesses potent diuretic, natriuretic, and vasorelaxant activities (De Bold, 1985). The discovery of ANP cast light on the heart as an endocrine organ involved in the control of blood pressure and body fluid homeostasis (Cantin and Genest, 1985; Kangawa et al., 1984; Needleman et al., 1985). Soon after the discovery of this peptide in the heart, investigations using radioimmunoassay (RIA) and immunohistochemistry revealed the existence of ANP in the central nervous system (CNS), and suggested the involvement of this peptide in the central regulation of cardiovascular homeostasis as a neurotransmitter or neuromodulation (Imura and Nakao, 1990; Nakao et al., 1986b; Quirion, 1988; Samson, 1987; Saper et al., 1985).