Correlation between Morpholoi;ical, Biochemical, and Biophysical Effects 



47 



Fig. 3. Cak 



The decreased adhesion of HeLa cells to the culture flask produced by PTH, 

 which may suggest a change in membrane properties, was investigated. One unit of 

 PTH/ml of medium increased the number of cells in suspension five fold from 

 62.0 ±7.2 to 346.0 ±9.1 //g cell protein in one hour (p< 0.001). To study whether 



these modifications were due to 



changes in calcium distribution be- 

 tween medium and cells, cultures 

 were grown for 6 days in media 

 containing -i^Ca and the decrease 

 in specific activity of the medium 

 analyzed at 2 hours, 3 and 6 days. 

 Fig. 3 shows that cellular uptake 

 of calcium is more than doubled 

 in PTH treated cells. Whether 

 this represents calcium bmdmg to 

 the membrane or calcium trans- 

 port has not yet been determined, 

 but viewed in the light of the ob- 

 servation that there is an optimal 

 calcium concentration below and above which cell adhesion decreases (Weiss, 1960), 

 the data may reflect a modification in the properties of the membrane. Since calcium 

 increases membrane resistance in a variety of systems, the action of PTH on the 

 electrical properties of the iso- 

 lated toad bladder was investigated. ^ ^ ...,.n... o.....,,, (300 



Bladders of Bu\o Mariniis were 

 mounted between Incite halfcham- 

 bers. Membrane potential and short 

 circuit current were determined 

 and the resistance was calculated. 

 One unit PTH/ml of Frog Ringer 

 was added on the serosal side in 

 the experimental group. Fig. 4 

 shows a drop in short circuit cur- 

 rent and no significant change in 

 potential. There was, therefore, a 

 concomitant rise in membranes re- 

 sistance. The results of 12 experi- 

 ments summarized in Table 2 could be interpreted in terms of a shift of calcium 

 from the extracellular fluid to the cell membrane induced by PTH and increasing 

 membrane resistance. 



Table 2. PTH on toad bladders 



HOURS 

 Fig. 4. Effects of 1 U. PTH ' 



Potential (mV) . . . 

 Short circuit current 



(uA) 



Resistance {Q) . . . 



32.2 



58.2 

 490 



33.0 



41.3 



712 



N. S. 



0.001 

 0.02 



