R N Chute — Page 2 | PubMed Health

Parabiosis of female rats with castrate males or oophorectomized females produces carcinoma of the breast in the majority of intact females. When unilateral nephrectomy of each partner is added to the procedure, the incidence is 100 percent. Radioimmunoassays for luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, estradiol and progesterone have been performed on the sera of these rats. The pathogenesis of the breast carcinomas is discussed in the light of these results. An attempt to weigh various factors thought to be involved in causing human and experimental rat cancer of the breast suggests significant differences of a quantitative nature.

Animals↗

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Effect of pheochromocytoma and hypophysectomy on blood pressure and catecholamines in NEDH rats.

The New England Deaconess Hospital (NEDH) rat provides a valuable model with which to study pheochromocytoma (P); 59% of male rats 700 to 900 days old and 81% of those 900 days or older developed spontaneous P. One transplantable P (P259), when implanted into other NEDH rats, markedly increased plasma norepinephrine and dopamine as well as blood pressure, and usually caused death within 4 weeks. Even without P, about 83% of NEDH rats became hypertensive by 131/2 weeks of age and remained moderately hypertensive until 2 years of age when some animals developed spontaneous P and hypertension became severe. Whether a common mechanism is responsible for early appearance of hypertension and later development of P remains to be determined. Hypophysectomized NEDH rats remained normotensive or slightly hypotensive despite marked elevations of plasma norepinephrine and dopamine caused by P259 implantation; furthermore, survival was prolonged to 3 months. Catecholamine concentrations in plasma and RBC were usually quite similar, indicating that red blood cells play a significant role in inactivating circulating catecholamines. Unlike the normal adrenal, P259 in NEDH rats contains mainly norepinephrine and dopamine with little epinephrine; it appears that P259 is deficient in the enzyme phenylethanolamine-N-methyltransferase (PNMT), which converts norepinephrine to epinephrine. Why hypophysectomy prevents hypertension and prolongs life in rats with P259 implants is unclear; adrenal cortical and thyroid deficiency may play a role. Preliminary observations indicate that hypophysectomy can prevent spontaneous development of P in NEDH rats.

Adrenal Gland Neoplasms↗