Effects of reduced milk intake on lymphocytes of neonatal rats.
Prolactin (PRL) is an immunoregulatory molecule. We previously reported that milk-PRL passes to the circulation of the neonatal rat and plays a role in neonatal immune system maturation. Neonatal rats that had ingested PRL-poor milk (bromocriptine treatment of the dam) from days 2-5 of life, showed changed patterns of immune system development. In order to rule out the possibility that these changes were due to reduced milk intake rather than to milk-PRL, in this current study we varied neonatal milk intake by adjusting litter size to 6 or 12 pups. At day 10, splenocytes and thymocytes were: 1. tested for in vitro proliferation to the mitogens phytohemagglutinin or to concanavalin A; 2. stained with monoclonal antibodies to surface differentiation antigens and analyzed by flow cytometry. We found that reduced milk intake (litter size of 12) led to decreased mitogen responsiveness, the opposite of what was seen after ingestion of PRL-poor milk. However, a reduction in milk had no significant affect on expression of surface differentiation antigens. Therefore, the changes in neonatal immune development following ingestion of PRL-poor milk cannot be attributed to a decrease in total milk volume.
Mastro
AM
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
Picciano
MF