Abstract
Using radioimmunoassay systems respectively specific for substance P (SP), somatostatin, motilin and VIP, distributions of these hormones in porcine, human, canine, monkey and tupaia tissues were investigated in terms of the immunoreactivities of the tissue extracts. The radioimmunoassay systems had been developed exclusively with highly purified synthetic polypeptides. SP, somatostatin and VIP immunoreactivities were found throughout the porcine intestinal extracts and remarkably high concentration of VIP was detected in the colon, 340pg/mg (wet weight of tissue). The largest amount of immunoreactive motilin was found in the porcine duodenum, 109pg/mg, and in the jejunum, 131pg/mg. The human gastrointestinal tract extracts were also found to contain high level of VIP immnoreactivity, especially in the duodenum, 286 and 270pg/mg, and jejunum, 225pg/mg. In the canine and monkey tissue extracts, immunoreactive SP, somatostatin and motilin were detected throughout the intestines, and the largest amounts of SP and somatostatin were found in the canine antrum, 2.7±2.0 and 38.9±17.9pg/mg, respectively, but significant quantities of the two hormones were also present in the duodenum, jejunum and colon of both the animals. Relatively high concentration of somatostatin-like immunoreactivity was detected in the lower part of jejunum and ileum. This concentration of immunoreactive motilin in the canine and monkey duodenum was significantly lower than that of porcine and human tissues. This may be partially due to the species variation in the primary structure of this hormone. In the case of the tupaia, the four kinds of hormone immunoreactivities were found throughout the intestinal tissue extracts, and the distribution patterns of them were similar to those in the canine and monkey tissues, although some variations were found in their concentrations. The level of immunoreactive SP in the tupaia tissue extracts was higher than that in the other animals examined. SP was also detected in the lung. As in the porcine case, the highest level of immunoreactive VIP, 150pg/mg, was found in the tupaia colon extracts. In the pancreas, all of the hormones examined were found and the amount of somatostatin immunoreactivity, which was relatively large, was of the same order as those of SP and VIP, but the concentration of immunoreactive motilin was considerably low, 3.1±1.0pg/mg. In the canine brain tissue extracts, relatively high concentration of immunoreactive SP, somatostatin and VIP was found, while the amount of immunoreactive motilin was extremely low. In the pituitary extracts, the concentration of immunoreactive motilin in the anterior lobe, 139.9±37.4pg/mg, was higher than that in the posterior, 70.8±18.6pg/mg, while SP-, somatostatin- and VIP-like immuroreactivities were rich in the posterior lobe, 184.4±44.6, 581.0±140.4 and 195.0pg/mg, respectively. These results revealed that SP-, somatostatin-, VIP- and motilin-like immunoreactivities are distributed in the manner characteristic to each of the hormones over the regions examined.
