Prokineticins (PKs), multifunctional secreted proteins, activate two endogenous G protein-coupled receptors (R) termed PK-R1 and PK-R2. It was suggested that PK1 acts selectively on the endothelium of endocrine glands, yet PK-Rs were also found in endothelial cells (EC) derived from other tissues. Therefore we examined here the characteristics of PK - system in EC derived from different vascular beds. Corpus luteum (CL)-derived EC (LEC) expressed both PK-R1 and PK-R2. In contrast, EC from the aorta (BAEC) only expressed PK-R1. Interestingly, also EC from brain capillaries (BCEC) expressed only PK-R1. The distinct pattern of PK-R expression may define EC phenotypic heterogeneity. Regulation of receptor expression also differed in BAEC and LEC: TNFα markedly reduced PK-R1 only in BAEC, but serum removal decreased PK-R1 in both cell types. Therefore, if cells were initially serum-starved, the anti-apoptotic effect of PKs was retained only in LEC. Yet, addition of PKs concomitant with serum removal enhanced the proliferation and survival of both BAEC and LEC. Immunohistochemical staining showed that in CL and aorta PK1 was expressed in smooth muscle cells in vessel walls, suggesting a paracrine mode of action. PK1 enhanced the net paracellular transport (measured by electrical resistance and Mannitol transport) in LEC but not in BAEC or BCEC. Collectively, these findings indicate that PKs serve as mitogens and survival factors for microvascular (LEC) and macrovascular (BAEC) EC. However, the distinct expression and function of PK receptors suggest different physiological roles for these receptors in various EC types.

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