Kininogen changes evoked in plasma by feeding, pseudo-alimentary, vagal and carbamylcholine stimulation of the rat

Changes in plasma total (BKg), low (LKg), or high (HKg) molecular weight kininogens are indirect means of studying the participation of kinins in biological processes. To investigate kinin involvement in digestive activity, rats fasted overnight, but given access to water, were allowed to feed for one hour. BKg levels increased by 18% (p less than 0.0001); LKg by 29% (p less than 0.01); HKg remained apparently unchanged. Changes were reversed after 120 min. Decreases in circulatory HKg are probably masked by a compensatory response of the organism aimed at rapidly re-establishing kinin precursor levels in the circulation following their consumption by parasympathetic activity accompanying feeding. This conclusion is based on observations showing that fasted rats submitted to sham-feeding caused by visual/olfactory stimulation by food, present extensive (61%) reduction (p less than 0.001) of HKg, but not of LKg. It is further supported by results demonstrating that electrical stimulation of the distal stump of the cut left abdominal vagus nerve, as well as intravenous administration of carbamylcholine, a parasympathomimetic drug, also produce these changes, all of which were prevented by prior atropinization of the experimental animals. These results open the way for investigations on a possible role of kinins in the control of post-prandial vascular changes.