Antigenic determinants of pituitary intermediate lobe: accessions to CSF

In bovine, the intermediate lobe is highly active and the holocrine secretion of its marginal cell layer forms a colloid-like substance housed in the intra-glandular cleft (residual lumen). Immunodiffusion of fractions of intraglandular colloid shows determinants sharing antigenic specificity with GH, FSH, CSF and serum immunoglobulins. The fractions tested by PAGE show determinants common to intraglandular colloid, CSF and serum albumin. The intraglandular cleft housing intermediate lobe colloid communicates by well defined channels passing through the intermediate lobe with the subarachnoid space, and with the cavernous sinuses by well defined venous channels. The venous channels are provided with well developed valve-like structures preventing venous blood from entering the cleft. These results question the relationship of the blood-brain barrier to the transport of pituitary substances. It is known that some pituitary peptide hormones (e.g. GH, ACTH, etc.) cannot cross the blood-brain barrier and their concentration in the CSF may not be due to an impairment of the barrier. We contend that intraglandular colloid of intermediate lobe origin is a part of major pituitary transport system and, fluctuating hormones and immunoglobulins in the CSF may be due to direct contributions from the pituitary.