QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Brommage, R. Search for Related Content PubMed PubMed Citation Articles by Brommage, R.

Measurement of Calcium and Phosphorus Fluxes During Lactation in the Rat^{1 ,2}

Division of Renal Medicine, Michael Reese Hospital and Medical Center, Chicago, IL 60616, and Department of Physiology, Chicago College of Osteopathic Medicine, Chicago, IL 60615

Novel, two-compartment metabolic cages for rats were constructed to examine Ca and P fluxes during lactation. Four consecutive balance studies of 4 d each were performed in lactating rats and nonlactating controls. Lactating rats had dramatically higher intestinal absorptions of Ca and P resulting from both increased food consumption and elevated fractional absorptions of these elements. Urinary Ca excretion was reduced during lactation whereas urinary P excretion was unchanged. Endogenous fecal Ca excretion (determined by infusing ⁴⁵Ca and dividing fecal ⁴⁵Ca content by urinary ⁴⁵Ca specific activity) was similar in lactating and nonlactating rats. In a separate study, pup retention of ingested Ca averaged 96%. Therefore, the difference in pup carcass Ca content between d 1 and 17 of age is assumed to equal 96% of the Ca transfer rate into milk. Similar calculations were applied to P. Milk transfer rates were determined to be 126 and 99 mg/d for Ca and P, respectively. These calculations indicate that 19% of the Ca transferred to milk was derived from the maternal skeleton with the maternal diet supplying the remaining Ca. This study provides the first comprehensive analysis of the alterations in Ca and P fluxes that occur during lactation in the rat.

KEY WORDS: • lactation • calcium • phosphorus • intestinal transport • urinary excretion • neonatal development

¹ Supported by NIH New Investigator Research Award AM37154/AR38784.

² Preliminary data were presented at the 8th Annual ASBMR Meeting in Anaheim, CA, June, 1986 [J. Bone Miner. Res., vol. 1; Suppl. 1, Abstract # 124, 1986]. Final data were presented at the 9th Annual ASBMR Meeting in Indianapolis, IN, June, 1987 [J. Bone Miner. Res., vol. 2; Suppl. 1, Abstract # 29, 1987].

³ Present address: Nestle Research Centre, CH-1350 Orbe, Switzerland.

Manuscript received 3 September 1987. Revision accepted 17 October 1988.