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FLUOROCHROME LABELING USING OSMOTIC MINIPUMPS.  B. Halloran¹, L Venton¹, G Evans², E Holton³, E Hill⁴, R Turner², T Wronski⁵, D Bikle¹. ¹ Division of Endo., Veteran Affairs Med. Ctr., San Francisco CA, ² Mayo Clinic, Rochester, MN, ³Ames Research Center, Moffett Field, CA, ⁴Lockheed Space Sciences, Moffett Field, CA, ⁵Depart. of Physiol. Sciences, Univ. of Florida, Gainsville.

   Automated delivery of bone fluorochrome labels could be invaluable in remote locations such as spaceflight.  We developed an automated system using polyethylene tubing attached to Alzet osmotic minimpumps to deliver calcein s.c. on 5d of a 12d study or d12 of an 18d study.  Polyethylene-60 tubing was cut to 6.55cm for d5 and 15.75cm for d12.  Tubing was sterilized, rinsed with fetal bovine serum, and filled with sesame oil (24ml for d5 and 66ml for d12), a small bolus (6ml) of calcein (2.5mg/kg) and then a small bolus (6ml) of sesame oil.  Tubing was attached to a saline filled osmotic pump.  Rats, 6 wks. or 6 mon. old, were sham operated or implanted with minipumps.  Three days after surgery, rats were divided into hindlimb unloaded or control groups.  Demeclocycline was injected, s.c., on day 0, and calcein was delivered s.c. on day 5 or 12.  Bone formation rate (BFR) was measured at the tibiofibular junction.
   BFR for 6 week control injected and pump were 31.5 ± 5.5 and 32.8 ± 6.5 mm²/day respectively and for unloaded 18.3 ± 0.9 and 20.1 ± 4.7 mm²/day.  BFR for 18 d 6 month control injected and pump were 2.3 ± 1.2 and 3.1 ± 1.6 mm²/day respectively and for unloaded 0.6 ± 0.9 and 0.9 ± 1.1 mm²/day. 
   BFRs were not significantly different between the animals receiving calcein by injection or minipump. These data demonstrate that minipumps can accurately deliver bone labels at the specified times and that the pump-tubing system could be utilized for many drugs/labels in various remote environments such as space.