PLASMA-CLEARANCE, TISSUE UPTAKE AND EXPRESSION OF PITUITARY PEPTIDE 23 PANCREATITIS-ASSOCIATED PROTEIN IN THE RAT/

The secretion of peptide 23 by rat pituitary cells is stimulated by gr owth hormone-releasing hormone and inhibited by somatostatin. Recent c loning of the cognate cDNA for peptide 23 revealed that it is identica l to pancreatitis-associated protein (PAP). In the present study, the clearance and tissue uptake of recombinant peptide 23/PAP in normal ad ult male rats was assessed. The plasma half-life of recombinant peptid e 23/PAP was 4.8 +/- 1.4 (S.D.) min. Maximal accumulation of radiolabe lled peptide 23/PAP was observed in the kidney, stomach, small intesti ne and pancreas whereas negligible uptake was seen in the liver, lung or heart. Peptide 23/PAP was detected in a variety of tissue extracts using a radioimmunoassay. Extracts of ileum contained the highest conc entrations of peptide 23/PAP. In situ hybridization analysis showed th at peptide 23/PAP mRNA was highly expressed in the columnar epithelial cells of ileum, jejunum and duodenum. These observations demonstrate that peptide 23/PAP, a protein previously thought to be of pituitary o rigin, is widely expressed in the gastrointestinal tract and that it i s rapidly removed from the circulation by the kidney and by tissues wh ich express peptide 23/PAP.