P. Vanbergen et al., CARDIOVASCULAR EFFECTS OF GAMMA-MSH ACTH-LIKE PEPTIDES - STRUCTURE-ACTIVITY RELATIONSHIP, European journal of pharmacology, 294(2-3), 1995, pp. 795-803
Intravenous administration of gamma(2)-melanocyte-stimulating hormone
(gamma(2)-MSH) to conscious rats causes a dose-dependent increase in b
lood pressure and heart rate, while the structurally related peptide a
drenocorticotropic hormone-(4-10) (ACTH-(4-10)) is 5-10 times less pot
ent in this respect. This prompted us to investigate which amino acid
sequence is determinant for the cardiovascular selectivity of peptides
of the gamma-MSH family. Lys-gamma(2)-MSH, most likely the endogenous
ly occurring y-MSH analog, was as potent as gamma(2)-MSH in inducing i
ncreases in blood pressure and heart rate. Removal of C-terminal amino
acids resulted in gamma-MSH-fragments which were devoid of cardiovasc
ular activities. Removal of amino acids from the N-terminal side of ga
mma(2)-MSH resulted in fragments which were less potent, but had an in
trinsic activity not different from that of gamma-MSH. Surprisingly, g
amma-MSH-(6-12) was more potent than gamma(2)-MSH. The shortest fragme
nt which displayed presser and tachycardiac responses was the MSH 'cor
e', His-Phe-Arg-Trp (=gamma-MSH-(5-8)), which is identical to ACTH-(6-
9). This was corroborated by testing fragments of ACTH-(4-10). We conc
lude that the message essential for cardiovascular effects resides in
the gamma-MSH-(5-8)/ACTH-(6-9) sequence. Proper C-terminal elongation
is required for full expression of cardiovascular activity of gamma(2)
-MSH, as the sequence of Asp(9)-Arg(10)-Phe(11) appears to play an imp
ortant role in establishing intrinsic activity. The amino acids N-term
inal to the MSH 'core' sequence appear to be essential for the potency
of the peptides.