Estrogen receptors (ER) and progesterone receptors (PgR) were studied immunohistochemically using specific antireceptor monoclonal antibodies in uterine tissue samples from 33 women in various stages of the menstrual cycle. Immunohistochemical localization was quantified as to intensity of staining and tissue distribution in glandular epithelium, stroma, and myometrium, and the results were compared with those of standard ligand binding assays. In all samples ER and PgR localized within the nuclei of target cells. The maximal concentrations of ER and PgR occurred in the mid- to late proliferative phase of the menstrual cycle. ER content declined throughout the secretory phase. In contrast, PgR content underwent unexpectedly complex and dyssynchronous fluctuations during the secretory phase of the menstrual cycle. Specifically, the glandular epithelium had diminished PgR content, while the stroma and myometrium maintained a significant PgR content. PgR and perhaps ER are not concordant in different cell types within the uterus. Segregation of function through alteration of receptor content may be an important mechanism in steroid-dependent growth and differentiation of target tissues.

Biomarkers of hydration change in response to acute dehydration; however, their responsiveness to changes in fluid intake volume, without exercise or heat exposure, has not been adequately described. Moreover, patterns of circadian variation in hydration biomarkers have not been established. The study aims were to (1) assess the response of hydration biomarkers to changes in daily water intake; and (2) evaluate circadian variation in urinary and salivary biomarkers. Fifty-two adults (24.8 ± 3.1 years; 22.3 ± 1.6 kg/m2; 79 % female), grouped based on habitual fluid intake (low drinkers, n = 30, <1.2 L/day; high drinkers, n = 22, >2.0 L/day), completed a 5-day inpatient crossover trial. On days 1 and 2, low drinkers received 1.0 L/day of water while high drinkers received 2.5 L/day. On days 3 through 5, intake was reversed between groups. Plasma and saliva osmolality were assessed daily at predetermined times, and all urine produced over 24 h was collected in timed intervals. ANOVA with intake (1.0 vs. 2.5 L/day), day, and time revealed that (1) urine concentration (osmolality, specific gravity, color) and volume, but not plasma nor saliva osmolality, responded to changes in water intake; (2) urinary hydration biomarkers and saliva osmolality vary as a function of the time of day; and (3) urine osmolality measured in samples collected during the afternoon most closely reflects the corresponding 24 h value. Overall, urinary hydration biomarkers are responsive to changes in water intake, and stabilize within 24 h of modifying intake volume. Moreover, short afternoon urine collections may be able to replace 24 h collections for more convenience in hydration assessment.

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