UPDATE 1-PAA Natural Gas Storage prices IPO at $19-$21 apiece

* IPO of 10 mln units at $19-$21/unit

* Sees proceeds of $187.8 mln

* To use proceeds to repay debt

April 22 (Reuters) - PAA Natural Gas Storage LP said it priced its initial public offering of 10 million common units at $19 to $21 apiece.

The operator of natural gas storage facilities expects to get $187.8 million in net proceeds, assuming the offering is priced at the mid-point of the price range.

PAA Natural Gas Storage LP, a wholly-owned subsidiary of Plains All American Pipeline LP (PAA.N), plans to use the proceeds, along with borrowing, to repay outstanding debt, it said in a filing with the U.S. Securities and Exchange Commission.

The company has applied to list its common units on the New York Stock Exchange under the symbol "PNG."

The Houston-based company owns and operates two natural gas storage facilities in Louisiana and Michigan and sometimes leases additional capacity and pipeline transportation from third parties. (Reporting by Anurag Kotoky in Bangalore; Editing by Don Sebastian)