Neurotransmitter-stimulated ion transport by cultured porcine vas deferens epithelium.

A collagenase-based dissociation technique has been developed to routinely establish monolayer cultures of freshly isolated porcine vas deferens epithelium. Cells isolated from each tissue are transferred to 25-cm(2) tissue culture flasks and grown in a standard cell culture medium. Flasks reach confluency in 3-4 days, and cells are subsequently seeded onto permeable supports. Cultured cells display a monolayer cobblestone appearance and are immunoreactive to anti-ZO-1 and anti-cytokeratin antibodies. Electron microscopy is employed to demonstrate the presence of junctional complexes and microvilli. When evaluated in modified Ussing chambers, cultured monolayers exhibit a basal lumen negative potential difference, high electrical resistance (>1,000 Omega. cm(2)), and respond to norepinephrine, vasopressin, ATP, adenosine, and histamine, with changes in short-circuit current indicative of anion secretion. Responses are significantly attenuated in Cl(-)- and/or HCO-free solutions. Attempts to further optimize culture conditions have shown that chronic exposure to insulin increases proliferation rates. Thus the culture method described will reliably produce viable neurotransmitter-responsive cell monolayers that will allow for the characterization of vas deferens epithelial function and associated control mechanisms.

Neuroglandular synapses in the pharynx of the sea anemone Aiptasia pallida (Cnidaria, Anthozoa).

Scanning and transmission electron microscopy of the pharynx of the sea anemone Aiptasia pallida revealed a heavily ciliated epidermis and two types of gland cells not known previously to be innervated. By tracing serial cross sections of the pharynx, we located and characterized two types of neuroglandular synapses (i.e., those having clear vesicles and those with dense-cored vesicles). The diameters of the vesicles at each synapse were averaged; clear vesicles ranged from 70 to 103 nm in diameter and were observed at synapses to both mucous and zymogenic gland cells. Dense-cored vesicles ranged from 53 to 85 nm in diameter and were observed at synapses to two mucous gland cells. One mucous gland cell had three neuroglandular synapses, one with clear vesicles and two with dense-cored vesicles. The occurrence of either clear or dense-cored vesicles at neuroglandular synapses suggests that at least two types of neurotransmitter substances control the secretion of mucus in the sea anemone pharynx. To date, only clear vesicles have been observed at a neurozymogenic gland cell synapse in the pharynx. No evidence of immunoreactivity to phenylethanolamine-N-methyl transferase was observed at neuroglandular synapses, suggesting that adrenaline is not a transmitter in the pharynx of A. pallida.

Neurotransmitter-stimulated ion transport across cultured bovine mammary epithelial cell monolayers.

Bovine mammary epithelial (BME-UV) and myoepithelial (BMM-UV) cell lines were acquired with the goal of developing an in vitro model of mammary epithelia for the study of ion transport. The bovine mammary cell lines were successfully cultured on commercially available permeable supports, and results suggest that mammary epithelial cells, but not myoepithelial cells, form tight junctions necessary to perform a barrier function. Electrogenic ion transport was not observed in basal conditions. Acute exposure to norepinephrine or forskolin caused prototypic increases in short circuit current accompanied by a reduction in transmural resistance indicative of anion secretion through a conductive pathway. Bumetanide and N-(4-methyphenylsulfonyl)-N'-(4-trifluoro-methylphenyl)urea, inhibitors of Na+/K+/Cl- cotransport and cystic fibrosis transmembrane conductance anion channels, respectively, reduced forskolin-stimulated ion transport. Amiloride, an inhibitor of epithelial sodium channels, had no effect on basal or forskolin-stimulated ion transport. However, naturally occurring and synthetic corticosteroids induced the expression of amiloride sensitive current indicative of sodium absorption. Chronic exposure to increased apical ionic strength and/or reduced carbohydrate concentration were associated with reduced transepithelial resistance although forskolin-stimulated ion transport was unaffected. These results demonstrate that neurotransmitters and steroid hormones act directly on bovine mammary epithelial cells to acutely and chronically modulate the volume and composition of their secretions. The in vitro system that we describe can be further exploited to characterize cellular and molecular mechanisms associated with mammary function in health and disease.