AJP - Endocrinology and Metabolism, Vol 262, Issue 2 E230-E233, Copyright © 1992 by American Physiological Society
Bone mineral loss during lactation occurs in absence of parathyroid tissue
D. W. Hodnett, H. F. DeLuca and N. A. Jorgensen
Department of Biochemistry, University of Wisconsin-Madison, College of Agricultural and Life Sciences 53706.
The requirement of parathyroid tissue for bone mineral loss during
lactation was investigated. Lactating rats parathyroidectomized (PTX) at
day 2 of lactation and consuming a 2% calcium diet are hypercalcemic and
hypophosphatemic at day 13 of lactation. The high-calcium diet supports
normal growth of pups nursing PTX mothers. PTX lactating rats mobilize bone
mineral to the same extent as euparathyroid lactating rats consuming the
same diet. Non-lactating PTX rats lose no bone mineral over a similar time
period, indicating lactation-specific bone mineral mobilization in the
absence of parathyroid tissue. PTX rats were verified to have
physiologically insignificant amounts of parathyroid tissue, as evidenced
by severe hypocalcemia and/or death in each rat after a shift from a 2%
calcium to a 0.02% calcium diet. These results conclusively demonstrate
that lactation-associated bone mineral mobilization does not require
parathyroid hormone or parathyroid tissue.
