Alpha-lactorphin lowers blood pressure measured by radiotelemetry in normotensive and spontaneously hypertensive rats

Life Sci. 2000;66(16):1535-43. doi: 10.1016/s0024-3205(00)00471-9.


Cardiovascular effects of subcutaneous administration of synthetic alpha-lactorphin, a tetrapeptide (Tyr-Gly-Leu-Phe) originally derived from milk alpha-lactalbumin, were studied in conscious spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY) with continuous radiotelemetric monitoring. Alpha-lactorphin dose-dependently lowered blood pressure (BP) without affecting heart rate in SHR and WKY. The lowest dose which reduced BP was 10 microg/kg, and the maximal reductions in systolic and diastolic BP (by 23+/-4 and 17+/-4 mm Hg, respectively) were observed at 100 microg/kg 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-lactorphin between SHR and WKY. Naloxone (1 and 3 mg/kg s.c.), a specific opioid receptor antagonist, abolished the alpha-lactorphin-induced reduction in BP and reversed it into a pressor response, which provides evidence for an involvement of opioid receptors in the depressor action of the tetrapeptide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin-Converting Enzyme Inhibitors / pharmacology*
  • Animals
  • Blood Pressure / drug effects*
  • Bradykinin / analogs & derivatives
  • Bradykinin / pharmacology
  • Captopril / pharmacology
  • Dose-Response Relationship, Drug
  • Hypertension / drug therapy*
  • Hypertension / physiopathology
  • Male
  • Naloxone / pharmacology
  • Oligopeptides / pharmacology*
  • Rats
  • Rats, Inbred SHR
  • Rats, Inbred WKY
  • Receptors, Opioid / drug effects
  • Receptors, Opioid / physiology


  • Angiotensin-Converting Enzyme Inhibitors
  • Oligopeptides
  • Receptors, Opioid
  • alpha-lactorphin
  • Naloxone
  • icatibant
  • Captopril
  • Bradykinin