The alveolar macrophage (AM), as a representative human tissue macrophage, was used in an in vitro system to examine the anti-human immunodeficiency virus type-1 (HIV-1) activity of zidovudine (AZT) and granulocyte-macrophage colony-stimulating factor (GM-CSF). AMs were infected with the IIIB strain of HIV-1 and exposed to AZT (1 mumol/L), GM-CSF (30 U/mL), a combination of AZT (1 mumol/L)/GM-CSF (30 U/mL), or medium control. At 10 or 20 days post-infection, phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear leukocytes (PBMLs) were added to the AM cultures as stimulated target cells. AZT effectively suppressed HIV replication and prevented transfer/amplification in target PBMLs as long as the drug was maintained in the medium. GM-CSF neither suppressed nor augmented HIV replication. The combination of AZT/GM-CSF was comparable with AZT alone in suppressing both the initial infection of AMs and the transfer to target PBMLs as long as the agents were maintained in the cultures. However, when the drugs were removed at the same time that PHA-stimulated PBMLs were added to the culture, the combination of AZT/GM-CSF was found to be more effective than AZT alone in preventing the transfer/amplification of HIV in the target lymphocytes. These results suggest that (1) AZT is effective in inhibiting HIV-1 infection in mononuclear phagocytes; (2) GM-CSF neither inhibits nor augments the replication of the IIIB strain of HIV in human AMs; and (3) the combination of AZT and GM-CSF may have an enhanced anti-HIV-1 activity compared with AZT alone. Clinical trials with the two agents in combination appear warranted.

Opercular epithelia from seawater-adapted killifish (Fundulus heteroclitus) were dissected with the nerve intact, mounted in Ussing-style membrane chambers and bathed in symmetrical saline solutions. Nerve stimulation rapidly inhibited transepithelial current (a measure of Cl- secretion rate) by 27.3+/-3.3 % (N=22), and the effect could be sustained for more than 10 min using intermittent pulse trains at 10 Hz. The effect was blocked in a dose-dependent manner by yohimbine, but not by propranolol, atropine or tubocurarine, indicating mediation by <IMG src="/images/symbols/&agr ;.gif" WIDTH= "9" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG="3">2-adrenergic receptors. The effect was also present, but significantly diminished, in opercular membranes from animals that had been transferred to sea water for 48 h (18+/-8.6 % inhibition, N=14). The resting current and the effect were absent in membranes from freshwater-adapted animals. The addition of clonidine (1.0 micromol l-1 serosal side) started to inhibit Cl- current after 40-60 s; immediately before this, at 30 s, there was a significant rise (P<0.05, N=14) in tissue inositol 1,4,5, -trisphosphate (InsP3) level, but no change at later times, compared with LiCl-treated control membranes and measured by radiolabeled receptor assay. The results indicate that seawater-adapted killifish can decrease their Cl- secretion rate through the action of the sympathetic nervous system, a response appropriate for the entry of estuarine fish to fresh water, and that the effect is mediated by <IMG src="/images/symbols/&agr ;.gif" WIDTH="9" HEIGHT="12" ALIGN="BOTTOM" NATURALSIZEFLAG="3">2-adrenoceptors via InsP3. The results imply that euryhaline fish entering fresh water can undergo an autonomic reflex reduction in salt secretion that does not require a stress response.