title: Alpha-lactorphin and beta-lactorphin improve arterial function in spontaneously hypertensive rats.
abstract: alpha-lactorphin (Tyr-Gly-Leu-Phe) lowers blood pressure in conscious adult SHR. This tetrapeptide is originally released from milk protein alpha-lactalbumin by enzymatic hydrolysis. In order to evaluate the antihypertensive mechanisms of alpha-lactorphin, the effects of the tetrapeptide on vascular function were investigated in (30-35 weeks old) spontaneously hypertensive rats (SHR) with established hypertension and age-matched normotensive Wistar-Kyoto (WKY) rats in vitro. In addition, we studied the vascular effects of another structurally related tetrapeptide, beta-lactorphin (Tyr-Leu-Leu-Phe), which originates from milk protein beta-lactoglobulin. Endothelium-dependent relaxation to acetylcholine (ACh) was reduced in mesenteric arterial preparations of SHR as compared to those of WKY. In SHR, the ACh-induced relaxation was augmented by alpha-lactorphin or beta-lactorphin. The role of nitric oxide (NO) is suggested, since this improvement was abolished by the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). Simultaneous potassium channel inhibitor tetraethylammonium (TEA) elicited no additional effect on the ACh-induced relaxation. The cyclooxygenase inhibitor diclofenac did not attenuate the augmented ACh relaxation induced by alpha-lactorphin or beta-lactorphin, suggesting that endothelial vasodilatory prostanoids were not involved in the effect of the tetrapeptides. Endothelium-independent relaxation to the NO donor sodium nitroprusside (SNP) was augmented in mesenteric arterial preparations of SHR by simultaneous beta-lactorphin. The tetrapeptides did not alter vascular responses in mesenteric arteries from WKY. In conclusion, both alpha-lactorphin and beta-lactorphin improved vascular relaxation in adult SHR in vitro. The beneficial effect of alpha-lactorphin was directed towards endothelial function, whereas beta-lactorphin also enhanced endothelium-independent relaxation.
authors.affiliation: Institute of Biomedicine, Pharmacology, BIOMEDICUM HELSINKI, P.O. Box 63, FIN-00014 University of Helsinki, Finland. marika.sipola@helsinki.fi
authors.forename: Marika
authors.initials: M
authors.lastname: Sipola
authors.forename: Piet
authors.initials: P
authors.lastname: Finckenberg
authors.forename: Heikki
authors.initials: H
authors.lastname: Vapaatalo
authors.forename: Anne
authors.initials: A
authors.lastname: Pihlanto-Leppälä
authors.forename: Hannu
authors.initials: H
authors.lastname: Korhonen
authors.forename: Riitta
authors.initials: R
authors.lastname: Korpela
authors.forename: Marja-Leena
authors.initials: ML
authors.lastname: Nurminen
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000188:drug therapy / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000959:Antihypertensive Agents; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009842:Oligopeptides; D014665:Vasodilator Agents; C102982:alpha-lactorphin; C102983:beta-lactorphin; D009599:Nitroprusside; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester