Pharmacokinetics of norethisterone following its oral administration and by spraying it nasally or sublingually to male bonnet monkeys

Inertial particle deposition in a monkey nasal mold compared with that in human nasal replicas

Information on nasal particle deposition is used in risk assessments for exposure to airborne particulate pollutants and for optimizing the delivery of therapeutic aerosols. Monkeys are commonly used to assess the therapeutic potential of inhaled substances and to a lesser extent the toxicity of inhaled xenobiotics. Yet no reliable measurements of the deposition efficiency of monkey nasal airways for particles >1 microm have been reported to date. The goals of this study were to measure the deposition efficiency (>1 microm) of a replica of monkey nasal airways and to investigate potential differences in nasal deposition between humans and monkeys by comparing results with similar measurements recently reported for human nasal replicas. The monkey nasal replica was an acrylic mold made from a postmortem cast of the nasal airways of a 12-kg, male rhesus monkey. Particle deposition in the monkey nasal mold was measured for monodisperse aerosols between 1 and 10 microm and constant inspiratory flow rates between 2 and 7 lpm. Total deposition efficiency increased from nearly 0 to 100% with increasing particle inertia and was uniquely determined by values of an inertial impaction parameter. The deposition efficiencies of the monkey replica agreed well with those of human nasal replicas when compared according to equivalent Stokes numbers based on minimum cross-sectional area. Results from this study could improve monkey-to-human extrapolation models and interpretations of data from particle toxicity and therapeutic aerosol studies using monkeys.

A role for nocturnal serum testosterone surge in regulating spermatogenesis in the adult non-human primate

Adult male bonnet monkeys exhibit nychthermeral rhythms in testosterone (T) secretion but the precise role of this heightened level of T secretion in regulating spermatogenesis is not known. Intranasal administration of microdoses (500 μg or 250 μg/day) of Norethisterone (IN-NET) to adult monkeys (n=6) at 1600 h each day selectively and completely suppressed the nocturnal surge levels of serum. T. Concomitant with this was a significant reduction (P<0.01) in serum LH but not FSH levels. DNA flow cytometric analysis of testicular biopsy tissue showed by week 10 of IN-NET treatment an arrest in meiotic transformation of primary spermatocytes (4C) to round/elongate (1C/HC) spermatids and by week 20 there was a complete absence of 4C, 1C and HC cells (with a relative accumulation in 2C cells). The accumulated meiotic (4C) cells at week 10 showed an increase (>80%,P<0.01) in coefficient of variation and a decrease in intensity of DNA-bound ethidium bromide fluorescence, parameters characteristic of degenerating 'apoptotic' subpopulation of germ cells. While two monkeys exhibited acute oligozoospermia 4 became azoospermic by 20 weeks of IN-NET treatment. A complete, qualitative reversal in the regressive changes in spermatogenesis and near-normal sperm output were apparent at the end of a 20-week recovery phase. These data demonstrate that prolonged, selective suppression of nocturnal surge levels of serum T secretion exerts a primary effect on meiosis in spermatogenesis leading to oligo/azoospermic status in adult bonnet monkeys.