Immunoreactive dynorphin in rat tissues and plasma

Distribution of immunoreactive dynorphin (ir-dyn) has been determined in rat tissues using a highly specific antiserum. Concentrations are highest in the pituitary, brain and spinal cord, as previously reported. In peripheral tissues highest levels occur in the stomach and upper intestine, but ir-dyn has also been detected in several other tissues, including heart and skeletal muscle. Unilateral vagotomy did not affect the amount of ir-dyn in heart or stomach, and denervation did not affect the amount in skeletal muscle. Gel permeation chromatography of the ir-dyn in gastrointestinal tract, heart, and skeletal muscle revealed a larger apparent molecular weight than that of the 17-residue dynorphin. Using octadecylsilyl-silica cartridges, it was possible to extract and concentrate ir-dyn from rat plasma. By gel permeation chromatography plasma immunoreactivity was found in two peaks, both of higher apparent molecular weight than dynorphin. This immunoreactivity was unaltered by hypophysectomy or adrenalectomy.