Plasma melatonin concentrations were measured throughout bouts of hibernation in marmots maintained in a short photoperiod (light-dark 8:16) and ambient temperature of 5 or 15 degrees C. Melatonin concentration was also measured in two animals maintained in constant darkness. As an animal entered hibernation, plasma melatonin concentrations dropped to basal levels when body temperature reached 25 degrees C, and they remained low until arousal. During deep hibernation plasma melatonin values did not vary significantly (P greater than 0.05) with respect to time of day or different ambient temperatures. With nocturnal arousal plasma melatonin levels were similar to euthermic night values. Lack of a plasma melatonin rhythm during hibernation suggests that the pineal gland is not temperature compensated during hibernation, and due to the low tissue temperature of the pineal the circadian pacemaker driving melatonin secretion is incapable of stimulating a rhythm.

Mammalian milk contains ceruloplasmin, but little is known about additional forms in which copper is provided the infant by this fluid. A human mammary epithelial cell line (PMC42) with the characteristics and hormone responsiveness of normal mammary cells (Michalczyk et al, J Histochem Cytochem 56: 389, 2008) was employed to begin to address this issue. Polarized PMC42 cell monolayers with tight junctions, grown in bicameral chambers with and without lactational hormones, were supplied with 64Cu‐labeled Cu attached to purified plasma proteins (albumin and alpha‐2‐macroglobulin) on the basal side. Apical secretions were collected at various times thereafter. Ultrafiltration and size exclusion chromatography (SEC) of the secretions indicated that 10‐30% of the 64Cu was attached to 3 components in the range of 1‐2 kDa. The rest was with major and minor components of ~160 and 800 kDa, respectively. The 800 and 1‐2 kDa components increased with hormone treatment. Stable Cu components of similar sizes were detected via SEC/HPLC directly coupled to ICP‐MS, but with domination of the low molecular weight forms. Ceruloplasmin was detected in the secretions by rocket immunoelectrophoresis. The results suggest that in addition to ceruloplasmin, several other forms of copper are secreted by mammary epithelial cells into the milk. Supported by PHS Grant No. RO1 HD 46949.