Ml. Nurminen et al., alpha-lactorphin lowers blood pressure measured by radiotelemetry in normotensive and spontaneously hypertensive rats, LIFE SCI, 66(16), 2000, pp. 1535-1543
Cardiovascular effects of subcutaneous administration of synthetic alpha-la
ctorphin, a tetrapeptide (Tyr-Gly-Leu-Phe) originally derived from milk alp
ha-lactalbumin, were studied in conscious spontaneously hypertensive rats (
SHR) and in normotensive Wistar Kyoto rats (WKY) with continuous radiotelem
etric monitoring. alpha-Lactorphin dose-dependently lowered blood pressure
(BP) without affecting heart rate in SHR and WKY. The lowest dose which red
uced BP was 10 mu g/kg, and the maximal reductions in systolic and diastoli
c BP (by 23+/-4 and 17+/-4 mm Hg, respectively) were observed at 100 mu g/k
g dose in SHR. No further reductions were obtained at a higher dose of 1 mg
/kg. There were no significant differences in the BP responses to alpha-lac
torphin between SHR and WKY. Naloxone (1 and 3 mg/kg s.c.), a specific opio
id receptor antagonist, abolished the alpha-lactorphin-induced reduction in
BP and reversed it into a presser response, which provides evidence for an
involvement of opioid receptors in the depressor action of the tetrapeptid
e.