Mass spectrometric detection of preproenkephalin A-derived peptides in bovine pituitary

Mass spectrometric analysis of neuropeptidergic systems in the human pituitary and cerebrospinal fluid

Neuropeptidergic systems have been studied in human tissues and fluids, which include the pituitary and lumbar cerebrospinal fluid, respectively. This paper reviews the qualitative and quantitative mass spectrometric analytical data obtained from three areas of study. Methionine enkephalin (ME) and beta-endorphin (BE) were quantified in the human pituitary by liquid secondary ion mass spectrometry (LSI MS)-tandem mass spectrometry. Corresponding stable isotope-incorporated synthetic peptide internal standards were used. Proenkephalin A and proopiomelanocortin produce ME and BE, respectively. The analysis of neuropeptides in macroadenomas demonstrated a decrease in both of those neuropeptidergic systems relative to controls. An analysis of prolactin-secreting microadenomas showed an increase in the proenkephalin A system. Mass spectrometry was also used to detect opioid peptide-containing proteins in the pituitary. Enzymes that process the precursors of proenkephalin A and tachykinin (substance P) neuropeptides were studied in human lumbar cerebrospinal fluid. Electrospray ionization mass spectrometry was used to characterize the molecular mass of each peptide product.

Alteration of opioid peptide concentrations in the rat pituitary following survivable closed head injury

Concentration changes of methionine enkephalin-like immunoreactivity (ME-li) and beta-endorphin-like immunoreactivity (BE-li) in the rat pituitary following diffuse brain injury were studied. Closed head injury was induced by a weight-drop trauma device (450 g x 2 m). The level of closed head injury used in this study altered the pituitary opioid peptide concentrations. The level of ME-li did not change in the experimental groups 3 hours, 10 hours, 24 hours, and 3 days after the trauma, but significantly increased by 34% 10 days after the trauma. BE-li remained constant 3 hours and 10 hours following the injury, increased by 48% at 24 hours, and remained at this level for 10 days after the trauma (44% at 3 days, and 40% at 10 days). The levels of ME-li and BE-li in the control sham-operated rats did not change during these times. The present measurements of BE-li and ME-li in the pituitary indicate that the opioid peptides that derive from two different neuropeptidergic systems, proopiomelanocortin (POMC) and preproenkephalin A, respectively, may participate in the pathophysiology of a closed head injury.