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Description:
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A newly synthesized growth hormone - releasing hormone (GH -RH ) was infused for one minute into the hypophysial portal vessels of the anterior pituitary of adult male rats . The somatotrophs were observed at ultrastructural level for morphological changes indicative of increased levels of emiocytosis and synthesis of new hormone . An identical experiment was done with the infusate being ouabain , a digitalis glycoside , which is a known pharmacological in -vitro secretagogue for growth hormone . At 1 , 15 , 30 , and 60 minutes following infusion , the animal's anterior pituitary glands were removed and prepared for electron microscopic examination . Somatotrophs displayed marked emiocytic activity at 1 and 15 minutes and slight emiocytosis at 30 and 60 minutes in both the ouabain and GH -RH infused animals . The rough endoplasmic reticulum (RER ) became dilated at 15 minutes and was maximally stimulated at 30 minutes in both groups . Activation of the Golgi complexes was observed at 15 and 30 minutes as evidenced by distended lamellae and formation of coated and smooth vesicles . At 30 and 60 minutes post -infusion , both the ouabain and GH -RH groups displayed an increase in dense lamellar bodies indicating an increase in lysosomal activity .
The findings from this study provide morphological evidence for the specificity of a new highly active GH -RH that stimulates both hormone synthesis and release in somatotrophs in -vivo . The morphological changes correspond to in - vitro and in - vivo studies with hypothalamic extracts and a commercially available decapeptide GH -RH . Ouabain stimulated both synthesis and release non -specifically in the anterior pituitary . |