PARATHYROID HORMONE-RELATED PROTEIN IN TISSUES OF THE EMERGING FROG (RANA-TEMPORARIA) - IMMUNOHISTOCHEMISTRY AND IN-SITU HYBRIDIZATION

Using antiserum to human parathyroid hormone-related protein (1-16) [P THrP(1-16)] we have examined tissues of the common frog (Rana temporar ia) for the presence of immunoreactive PTHrP (irPTHrP) at the stage of emergence from water to land. irPTHrP was detected in dorsal and vent ral stratum granulosum of the skin, in the developing ovary, striated muscle and the choroid plexus epithelium of the brain as well as in th e olfactory gland epithelium and olfactory lobe neurons of the brain. In the pituitary and hypothalamus irPTHrP protein could be demonstrate d in the median eminence, infundibular stem and principally in the neu ral lobe and pars distalis of the pituitary with weak reaction in the pars intermedia. In situ hybridisation of the same tissues with an oli gonucleotide probe to chicken PTHrP 55-65 clearly showed the presence of mRNA for PTHrP-like molecule in all the tissues containing irPTHrP. There was a major inconsistency in the pituitary in that the highest level of gene expression, assessed by in situ hybridisation, was found in the pars intermedia with only very low expression in the pars dist alis and neural lobe and undetectable levels in the infundibular stem and median eminence. These observations suggest that tissues of the fr og synthesise a PTHrP-like molecule but that in the pituitary the pars intermedia cells may export the protein to cells in other regions of the pituitary and hypothalamus.