Journal of Applied Physiology, Vol 73, Issue 2 458-464, Copyright © 1992 by American Physiological Society
Ontogeny of integumental calcium in relation to surface area and skin water content in the perinatal rat
S. B. Hoath, W. L. Pickens, R. Tanaka and R. Ross
Department of Pediatrics, Children's Hospital Medical Center, Cincinnati, Ohio 45229-2899.
Calcium is an important regulator of epidermal differentiation and skin
biomechanics in many vertebrate species. In this study, we measured total
epidermal calcium in the perinatal Sprague-Dawley rat. Values ranged from
12 to 15 mg per 100 g of tissue. These levels were elevated compared with
dermis and other soft (nonbone) organs, including brain, kidney, heart, and
liver. Administration of radioactive calcium to the pregnant rat resulted
in high rates of 45Ca2+ localization in the fetal epidermis 24 h later.
From gestational day 20 to postnatal day 3, the epidermis showed
progressive dehydration with water content decreasing from 79 to 73%.
Dermal hydration over the same period decreased from 91 to 81%. In the
neonatal rat (age 0-3 days), linear regression analysis of surface area vs.
body weight on a log-log plot yielded a slope of 1.04. This finding
contrasts with an expected slope of 0.67 based on simple surface
area-to-volume relationships and differs from the empirical 0.75-power law
observed in adult bioenergetics. In summary, these results show the
perinatal rat is encapsulated by a continuous differentially hydrated
calcium-rich epidermal envelope that increases in surface area over the
early postnatal period directly as the first power of body mass.
