Endocrine Abstracts

Ghrelin is expressed in endothelial cells but its precise role remains unknown. Some authors treat ghrelin as an endogenous regulator of angiogenesis.

The aim of this study was to examine the direct effect of human acylated and unacylated ghrelin and rat acylated ghrelin applied alone or together with D-Lys-GHRP-6, an antagonist of ghrelin receptor type 1a, on the growth of murine endothelial cell line HECa10 assessed by Mosmann method in vitro.

Human ghrelin is homologous to rat ghrelin apart from two amino acids, but their effects on the growth of the examined line differ significantly. Human acylated and unacylated ghrelin inhibited the growth of HECa10 line at all examined concentrations (10⁻⁵–10⁻¹² M) in 24 h and 72 h culture with almost the same potency. Rat acylated ghrelin inhibited the growth of this line only at 2 out of 8 concentrations (10⁻⁷, 10⁻¹¹ M) in 24 h culture and at 3 out of 8 concentrations (10⁻⁷, 10⁻⁸, 10⁻¹¹ M) in 72 h culture. D-Lys-GHRP-6 used as an antagonist of ghrelin receptor type 1a applied alone also inhibited the growth of this cell line at all examined concentrations (10⁻⁴–10⁻⁶ M) in 48 h culture in dose-dependent manner, and in 72 h culture without dose–response effect. D-Lys-GHRP-6 did not modify the inhibitory effect of rat acylated ghrelin in 48 h culture, but in 72 h culture we observed even stronger inhibitory effect of this combination in comparison with the effect of each substances applied alone. Unexpectedly D-Lys-GHRP-6 at the concentration of 10⁻⁴ M decreased, abolished or even reversed the inhibitory effect of human unacylated ghrelin in 72 h culture dependent on the ghrelin concentrations.

These data indicate that both ghrelins have an antiangigenic properties. However, D-Lys-GHRP-6 seems not to be an appropriate antagonist of ghrelin receptor type 1a in this experiment.