13357
Blood Na ( + ) levels remained relatively stable in all tested animals , but gill NKA activities were lower in eels exposed to combined stress .
 Chemical: Na ( + )
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: Na ( + ) 
Answer:
 Chemical: Na ( + )