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A new specific method for determination of cholecystokinin, CCK-8, and CCK-33, 39 in rat plasma is described. Plasma CCK radioimmunoassay (RIA) is difficult, because of cross-reactivity with gastrin. In the rat, problems because of difficulties in separating gastrin from CCK by high performance liquid chromatography (HPLC) exist. These were solved by enzyme digestion of gastrin before HPLC separation of molecular variants of CCK from gastrin fragments. Cholecystokinin immunoreactive forms in the HPLC fractions were determined by an antibody, which recognises the carboxyl terminus of CCK and gastrin. Fasting concentrations of small (CCK-8) and large (CCK-33, 39) molecular forms of CCK averaged 1.9 (0.3) pM and were raised to 13.4 (3.8) pM in rats fed ad libitum. Cholecystokinin in lactating rats rose two-fold after suckling, compared with 2.8 fold in response to feeding. The basal ratio between CCK-8 and CCK-33, 39 was approximately 1:1, but increased in favour of CCK-8 after feeding and in response to suckling. Gastrin like immunoreactivity measured in unextracted plasma was found to rise after feeding, but was unchanged in response to suckling. [ABSTRACT FROM PUBLISHER]

A new polypeptide hormone candidate regulating vascular smooth muscle function was extracted from porcine atrial tissue. The purification steps were followed by a bioassay. The hormonally active substance has been analyzed and found to be a small polypeptide exhibiting a molecular weight of about 7500 and is named 'cardiodilatin' (CDD). Further chemical data on this new hormone will be published elsewhere. A partial amino acid sequence of cardiodilatin is offered and shows that among the well known hormones or neuropeptides, none exhibit a homologue partial sequence. [ABSTRACT FROM AUTHOR]

A peptide hormone was extracted from the porcine right atrium following a bioassay for differential vaso-relaxant effects on smooth muscle strips from aorta and renal and inferior mesenteric arteries. The isolation procedure included several steps of gel-permeation and ion-exchange chromatography, and high performance liquid chromatography. During the isolation procedure, other peptides of smaller molecular weight were also found, which, in relation to cardiodilatin-126 (CDD-126), are shorter at their N-terminal. Among these, CDD-88 has also been isolated and characterizied, and has been established as a prominent member of the cardiac hormone family. The N-terminal and C-terminal segments of the 126 amino acid-containing molecule were synthesized and used to raise region-specific antibodies. The natural peptide was then localized within myoendocrine cells of the right atrium where specific atrial granules are located. Renal effects of cardiodilation were studied in conscious dogs and showed strong diuretic and natriuretic activities. According to our functional studies, cardiodilatin-126 and cardiodilatin-88 possess qualities of a significant hormone family regarding the regulation of extracellular fluid volume and blood pressure. [ABSTRACT FROM AUTHOR]