Quantification of the permeability of the blood-CSF barrier to alpha-MSH in the rat.
The ability of alpha-MSH to cross the blood-CSF barrier of the rat was assessed by measurement of the rate of appearance of immunoreactive alpha-MSH in a cerebrospinal fluid (CSF) perfusate following intravenous injection of peptide. Comparisons were made with the rate of appearance of a simultaneously administered dose of 14C-inulin which is poorly permeable at the blood-CSF barrier. Concentrations of drugs measured in plasma were fitted to two-compartment pharmacokinetic models, and those measured in the CSF perfusate to one-compartment open systems receiving an input from the plasma compartment. The rate constant for entry of alpha-MSH into CSF was 0.00087 min-1, which was not significantly different from that for inulin of 0.00055 min-1. As alpha-MSH penetrated into CSF at a rate comparable to inulin, it was concluded that the limited entry of peptide was by aqueous diffusion along with other water-soluble macromolecules.
D000818:Animals; D007275:Injections, Intravenous; D007444:Inulin; D007700:Kinetics; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000008:administration & dosage / Q000097:blood / Q000134:cerebrospinal fluid*; D010539:Permeability; D051381:Rats; D011919:Rats, Inbred Strains
D009074:Melanocyte-Stimulating Hormones; D007444:Inulin