The metastasis suppressor kisspeptin shows potent inotropic effects in rodent heart with lack of activity in the KISS1 (GPR54) knockout mouse

Helen Kirby, Janet Maguire, W.H. Colledge, Xavier d’Anglemont de Tassigny, Anthony Davenport. University of Cambridge, Cambridge, United Kingdom.

KISS1, the G-protein coupled receptor paired with kisspeptin in (Ohtaki et al., 2001), has roles as a metastasis suppressor, a gatekeeper of puberty and in placentation (Mead et al., 2007a). We have previously reported kisspeptin to additionally have potent vasoconstrictor actions in human coronary artery and umbilical vein (Mead et al., 2007b). Here we demonstrate the kisspeptin/KISS1 system to be expressed in the rodent cardiovascular system and that kisspeptin is a potent positive inotrope in atria.

Immunohistochemistry was performed on cryostat-cut heart sections (n = 3) from male C57/BL6 mice (20-30g) and male Sprague Dawley rats (200-220g), euthanised by CO2 inhalation, with anti-KISS1 and anti-kisspeptin antisera. Saturation binding analysis was performed on cryostat-cut sections of rat heart (n = 6) using 4pM–2nM [125I]-KP-14 with 1μM included to define non-specific binding. For in vitro pharmacology, paired atria from male Wistar rats (220-280g) and male 129S6/SvEv mice (20-30g) were set up in organ baths and paced by field stimulation (1Hz, 5ms duration, <4V). Tension on the tissue was adjusted to 50% of optimum resting tension before construction of cumulative concentration response curves to kisspeptin and termination by CaCl2 addition (6.7 mM). Agonist responses were expressed as %CaCl2 and data are mean ± s.e.mean.

KISS1-like immunoreactivity (LI) was detected in both endothelial and smooth muscle cells of intramyocardial blood vessels and cardiomyocytes of rodent heart. Kisspeptin-LI was observed in vascular and endocardial endothelial cells. Saturation binding analysis revealed saturable binding in rat heart: KD = 0.44±0.14nM and Bmax = 11.1±2.2 fmol/mg (n = 6). Kisspeptin elicited positive inotropic effects in rat (n = 4) and mice (n = 6) atria (pD2 = 9.9±0.6;10.2±0.3 and Emax = 14±2 %CaCl2;26±4 %CaCl2 respectively) which were absent in mice with targeted disruption of the gene encoding the KISS1 receptor.

In conclusion, we have shown kisspeptin and its receptor KISS1 to be expressed in the rodent heart and also to possess potent inotropic activity, comparable to that previously observed in human. Absence of these effects in mice lacking the KISS1 receptor indicates the presence of only one kisspeptin receptor in these species.

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