Plasma concentrations of immunoreactive proopiomelanocortin peptides and cortisol in clinically normal cats

We measured immunoreactive (IR) plasma concentrations of the proopiomelanocortin (POMC)-derived peptides (adrenocorticotropic hormone [ACTH]; beta-endorphin/beta-lipotropin [beta END/beta LPH]; and alpha-melanocyte stimulating hormone [alpha MSH]) and of cortisol in 100 clinically normal cats. Median plasma concentration of IR-ACTH was 2.7 pmol/L (range, < or = 1.1 to 22 pmol/L), of beta END/beta LPH was 28 pmol/L (range, 3.8 to 130 pmol/L), of alpha MSH was 36 pmol/L (range, < or = 3.6 to 200 pmol/L), and of cortisol was 35 nmol/L (range, 5 to 140 nmol/L). Plasma concentrations of IR-ACTH, alpha MSH, and beta END/beta LPH were at or below the assay sensitivity in 34, 3, and 0% of the cats, respectively. We did not detect a correlation between plasma concentrations of IR-ACTH and beta END/beta LPH (r = 0.23) or between plasma concentrations of IR-ACTH and alpha MSH (r = 0.19). However, there was a significant (P < 0.001) correlation between plasma concentrations of IR-beta END/beta LPH and alpha MSH (r = 0.81). There was not a significant correlation between plasma concentration of cortisol and plasma concentration of any of the IR-POMC peptides. High plasma concentrations of IR-alpha MSH and beta END, POMC peptides secreted predominantly by melanotrophs in other species, indicate that clinically normal cats have an actively secreting pars intermedia.(ABSTRACT TRUNCATED AT 250 WORDS)