Ontogenesis of monoamine oxidase and catechol-O-methyl transferase in various tissues of domestic swine.

Activities of monoamine oxidase (MAO) and catechol-o-methyl transferase (COMT) in liver, kidney, heart, spleen, hindbrain, and adrenal glands were compared in adult dogs, cats, guinea-pigs, rabbits, rats, sheep, and 150-day-old swine. Swine had the highest COMT activity and dogs or cats, the lowest in most tissues. MAO was more tissue and species variable. The ontogenesis of MAO or COMT was evaluated in the same six tissues of swine from 10 days before birth through 150 days of age. COMT and MAO generally increased in swine kidney and liver with age, but the developmental patterns were more variable in other tissues. COMT increased in heart, spleen, and adrenals through 14 days of age, decreased in spleen and adrenals to 150 days, but remained elevated in heart. Brain MAO activities were near or above 150-day-old levels at birth and changed little with age. Cardiac MAO fell from birth to 70 days of age, while splenic and adrenal activities increased with age. MAO substrate specificity to tyramine, benzylamine, and serotinin along with selective inhibition by harmine, pargyline, and clorgyline were used as indices of multiple enzymic forms. Type B MAO may dominate in all swine tussues except spleen, although the biochemical characteristics of this enzyme form do not seem to fit all of the patterns described for other species. Thermal stability of MAO in swine resembles that in the guinea-pig.