Aims and Methods: 

Pituitary adenylate cyclase activating polypeptide (PACAP) is an important neuropeptide with neurotrophic actions. We have recently shown that PACAP is present in the human milk in much higher concentration than in the plasma of lactating women. We found similar results in domestic animals (cow, sheep, goat). We showed the presence of PACAP38-like immunoreactivity in the homogenates of sheep mammary gland samples and we also detected PAC1-receptor expression in these lactating udder biopsies by fluorescent immunohistological examination. The aim of the first part of the study was to examine the PACAP level of human milk with radioimmunoassay (RIA) during 16 months of lactation. In the second part of the study we compare the presence of PAC1-receptors in the lactating and non-lactating udder biopsies of sheep.

Results: 

No significant difference was found between PACAP levels determined by RIA in the milk samples during the first 10 months of lactation. However, after that time a significant increase was observed compared to the samples from the first tree months. The immunohistological examination of mammary gland samples showed significantly increased PAC1-receptor immunopositivity in lactating samples compared to non-lactating samples.

Conclusion: 

The increased level of PACAP in the milk after the 10^th months could be due to the decreased amount of milk production and thus, the increased PACAP concentration is a compensation. The increased presence of PAC1-receptors in lactating mammary gland samples also indicates the important roles of PACAP in the lactation, the physiological implications of which awaits further investigations.

Support: 

OTKA K72592, F67830, 73044, CNK78480, ETT278-04/2009, Bolyai Scholarship, Richter Foundation, PTE AOK 2009 Research Grant