Abstract
There have been few studies of blood and plasma volumes in myxedema or experimental hypothyroidism, none on the rat. Thompson 1 in an early study found the plasma volume in myxedematous patients to be 30% below normal, and also found that the values returned to normal upon treatment with thyroid extract. Holböll 2 likewise found the blood and plasma volume reduced in myxedema. In the most recent study, Gibson and Harris 3 studied 7 myxedematous patients. They found that the blood volume was only 15% below normal, and attributed the lower results of earlier authors to errors in the method of blood volume determination used.
Methods. This study utilized 16 male rats, ranging in weight from 150 to 180 g at the start. Thyro-parathyroidectomy was performed, under ether anesthesia, by blunt dissection and cauterization of the thyroid bed. Following this, an interval of 3 weeks elapsed, during which the rats were undisturbed and were fed upon stock diet. At the end of 3 weeks, the rats had failed to gain weight in accordance with the normal growth curve. Blood and plasma volume determinations were performed according to the hemoglobin dye method previously described. 4 Gross post-mortem examination showed no regeneration of thyroid tissue at the site of operation. The heart weights were diminished in accordance with previous experience upon thyro-parathyroidectomized rats. 5
Results. Plasma volumes were obtained in 16 rats, and blood volumes were obtained in 14 of these. There was a mean reduction of plasma volume, erythrocyte volume and total blood volume of approximately 10%, when compared with normal standards for rats of the same weight, as previously established. 4 (Table I).
Get full access to this article
View all access options for this article.