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C McLean

Publications and source records attributed to C McLean.

80 records · Page 5Linked to original sources
PubMedDate not supplied

Pro-gamma-melanocyte-stimulating hormone cleavage in adrenal gland undergoing compensatory growth.

Regulation of the rapid compensatory growth seen in the remaining adrenal gland of rats following unilateral adrenalectomy is poorly understood. The role of adrenocorticotropic hormone (ACTH) is obscure as immunoneutralization of circulating ACTH does not affect the observed compensatory growth or hyperplasia. This finding, together with the fact that mechanical manipulation of one adrenal without extirpation is followed by growth only in the contralateral gland, has led to the concept of neural regulation of compensatory adrenal growth via a loop from one adrenal through the hypothalamus and back to the contralateral gland which is independent of ACTH secretion. We recently showed that peptides from the N terminal of ACTH precursor proopiocortin (POC), not containing the gamma-melanocyte-stimulating hormone (gamma-MSH) sequence, can stimulate adrenal mitogenesis and proposed that normal long-term adrenal growth and proliferation involves post-secretional proteolytic cleavage of pro-gamma-MSH [or N-POC(1-74)] to generate the mitogenic factor N-POC(1-48/49) and a C-terminal fragment N-POC(50-74), or rat gamma 3-MSH. We have now investigated this hypothesis further in rats by selectively quenching different regions of circulating POC peptides with specific antisera and observing the effect on the increases in weight, RNA and DNA normally seen in the remaining gland following unilateral adrenalectomy. Our results, reported here, suggest that neurally mediated proteolytic cleavage of the circulating inactive mitogenic precursor pro-gamma-MSH at the adrenal gland is the major mechanism of control of compensatory growth.

Adrenal Glands↗
PubMedDate not supplied

Conjugation of dinitrofluorobenzene to plasma proteins in vivo in the rat.

The extent of protein dinitrophenylation was determined in plasma and other tissues of anesthetized rats after administration of the model immunogen [3H]dinitrofluorobenzene (DNFB) (25 mg/kg; 5-25 microCi). DNFB was given by the intravenous, intraportal, intramuscular, or oral route. Irreversible binding was determined radiometrically after exhaustive solvent extraction of plasma or organ proteins. The extent of binding was high in plasma after parenteral administration (approximately 1% dose/ml plasma), but less (approximately 0.1% dose/ml) if DNFB was given orally. Low levels of radioactivity were bound irreversibly in liver (0.01-0.13% dose/g) and kidney (0.03-0.10% dose/g) and only residual amounts in other organs. Western blotting was used to identify target proteins in plasma, liver, and kidney using a specific antidinitrophenyl antiserum. No dinitrophenylation could be detected in liver or kidney samples, but strong recognition of two protein bands was observed in plasma. Bands with the same apparent molecular masses (67 and 44 kDa) were seen when DNFB was incubated with rat plasma in vitro. Preliminary evidence for these proteins being albumin and alpha 1-acid glycoprotein, respectively, is presented. The latter may be important for interindividual variability in immune responsiveness, because it is an acute phase protein whose levels fluctuate widely during disease states.

Animals↗